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Respirable aerosols (< 5 µm in diameter) present a high risk of SARS-CoV-2 transmission. Guidelines recommend using aerosol precautions during aerosol-generating procedures, and droplet (> 5 µm) precautions at other times. However, emerging evidence indicates respiratory activities may be a more important source of aerosols than clinical procedures such as tracheal intubation. We aimed to measure the size, total number and volume of all human aerosols exhaled during respiratory activities and therapies. We used a novel chamber with an optical particle counter sampling at 100 l.min -1 to count and size-fractionate close to all exhaled particles (0.5-25 µm). We compared emissions from ten healthy subjects during six respiratory activities (quiet breathing; talking; shouting; forced expiratory manoeuvres; exercise; and coughing) with three respiratory therapies (high-flow nasal oxygen and single or dual circuit non-invasive positive pressure ventilation). Activities were repeated while wearing facemasks. When compared with quiet breathing, exertional respiratory activities increased particle counts 34.6-fold during talking and 370.8-fold during coughing (p < 0.001). High-flow nasal oxygen 60 at l.min -1 increased particle counts 2.3-fold (p = 0.031) during quiet breathing. Single and dual circuit non-invasive respiratory therapy at 25/10 cm.H 2 O with quiet breathing increased counts by 2.6-fold and 7.8-fold, respectively (both p < 0.001). During exertional activities, respiratory therapies and facemasks reduced emissions compared with activities alone. Respiratory activities (including exertional breathing and coughing) which mimic respiratory patterns during illness generate substantially more aerosols than non-invasive respiratory therapies, which conversely can reduce total emissions. We argue the risk of aerosol exposure is underappreciated and warrants widespread, targeted interventions., (© 2021 Association of Anaesthetists.)

Background: Studies of potential adverse effects of traffic related air pollution (TRAP) on allergic disease have had mixed findings. Nutritional studies to examine whether fish oil supplementation may protect against development of allergic disease through their anti-inflammatory actions have also had mixed findings. Extremely few studies to date have considered whether air pollution and dietary factors such as fish oil intake may interact, which was the rationale for this study., Methods: We conducted a secondary analysis of the Childhood Asthma Prevention Study (CAPS) birth cohort, where children were randomised to fish oil supplementation or placebo from early life to age 5 years. We examined interactions between supplementation and TRAP (using weighted road density at place of residence as our measure of traffic related air pollution exposure) with allergic disease and lung function outcomes at age 5 and 8 years., Results: Outcome information was available on approximately 400 children (~ 70% of the original birth cohort). Statistically significant interactions between fish oil supplementation and TRAP were seen for house dust mite (HDM), inhalant and all-allergen skin prick tests (SPTs) and for HDM-specific interleukin-5 response at age 5. Adjusting for relevant confounders, relative risks (RRs) for positive HDM SPT were RR 1.74 (95% CI 1.22-2.48) per 100 m local road or 33.3 m of motorway within 50 m of the home for those randomised to the control group and 1.03 (0.76-1.41) for those randomised to receive the fish oil supplement. The risk differential was highest in an analysis restricted to those who did not change address between ages 5 and 8 years. In this sub-group, supplementation also protected against the effect of traffic exposure on pre-bronchodilator FEV 1 /FVC ratio., Conclusions: Results suggest that fish oil supplementation may protect against pro-allergic sensitisation effects of TRAP exposure. Strengths of this analysis are that supplementation was randomised and independent of TRAP exposure, however, findings need to be confirmed in a larger experimental study with the interaction investigated as a primary hypothesis, potentially also exploring epigenetic mechanisms. More generally, studies of adverse health effects of air pollution may benefit from considering potential effect modification by diet and other factors., Trial Registration: Australia New Zealand Clinical Trial Registry. www.anzctr.org.au Registration: ACTRN12605000042640 , Date: 26th July 2005. Retrospectively registered, trial commenced prior to registry availability.

Elephant-mediated transmission of tuberculosis is assumed to be similar to human models, which state close and prolonged contact with an infected individual is required for transmission. Although considered a risk factor for infection, several case studies have reported that close contact with an elephant is not always necessary for transmission, and the role of aerosolized bacteria remains unclear. To investigate aerosol-mediated transmission of pathogenic bacteria from elephants, a method for the detection of aerosols using an adapted sampling system was developed. A commensal bacterium was isolated from the upper respiratory tract of elephants ( Elephas maximus ) and was used as a proxy organism to detect aerosolized droplets in the sampling system. It was found that elephants are capable of producing aerosolized bacterial particles of a size small enough to remain airborne for prolonged periods and penetrate the lower regions of the human respiratory tract.

The clinical importance of peanut (Arachis hypogaea) allergies demands standardized allergen extraction protocols. We determined the effectiveness of common extraction conditions (20 buffers, defatting reagents, extraction time/temperatures, processing, extraction repeats) on crude protein and Ara h 1 and 2 yields. Despite similar 1D-gel profiles, defatting with n-hexane resulted in significantly higher yields of crude protein, Ara h 1, and Ara h 2 than with diethyl ether. The yields were affected by the composition and pH of the extraction buffers and other conditions, but crude protein yield did not always correlate with Ara h 1 and 2 yields. Denaturants, reducing agents, acidic buffers, and thermal processing of peanuts perturbed allergen quantification in ELISAs, probably via exposure of additional epitopes. Allergen detection in 2D-Western blots with PBS resulted in greater sensitivity than with TBS or Tris. We recommend that allergen extraction conditions be selected based on the research question being investigated., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Allergic diseases such as asthma and rhinitis are common in many countries. Globally the most common allergen associated with symptoms is produced by house dust mites. Although the bed has often been cited as the main site of exposure to mite allergens, surprisingly this has not yet been directly established by measurement due to a lack of suitable methods. Here we report on the development of novel methods to determine the pattern of personal exposure to mite allergen bioaerosols over 24-hour periods and applied this in a small field study using 10 normal adults. Air was sampled using a miniature time-based air-sampler of in-house design located close to the breathing zone of the participants, co-located with a miniature time-lapse camera. Airborne particles, drawn into the sampler at 2L/min via a narrow slot, were impacted onto the peripheral surface of a disk mounted on the hour-hand of either a 12 or 24 hour clock motor. The impaction surface was either an electret cloth, or an adhesive film; both novel for these purposes. Following a review of the time-lapse images, disks were post-hoc cut into subsamples corresponding to eight predetermined categories of indoor or outdoor location, extracted and analysed for mite allergen Der p 1 by an amplified ELISA. Allergen was detected in 57.2% of the total of 353 subsamples collected during 20 days of sampling. Exposure patterns varied over time. Higher concentrations of airborne mite allergen were typically measured in samples collected from domestic locations in the day and evening. Indoor domestic Der p 1 exposures accounted for 59.5% of total exposure, whereas total in-bed-asleep exposure, which varied 80 fold between individuals, accounted overall for 9.85% of total exposure, suggesting beds are not often the main site of exposure. This study establishes the feasibility of novel methods for determining the time-geography of personal exposure to many bioaerosols and identifies new areas for future technical development and clinical applications.

Much of what is known about the seasonality of human rhinovirus (hRV) infections has been learned from the study of acute asthma exacerbations presenting to emergency care, including those among children at the start of the school term. Much less is known about the patterns of hRVs in the community. In this study, viruses and day-to-day symptoms of asthma and colds were monitored twice weekly in 67 children with asthma aged 5-12 years, over a 15 month period in Sydney, Australia. Overall hRV was detected in 314/1232 (25.5%) of nasal wash samples and 142/1231 (11.5%) of exhaled breath samples; of these, 231 and 24 respectively were genotyped. HRVs were detected with similar prevalence rate throughout the year, including no peak in hRV prevalence following return to school. No peaks were seen in asthma and cold symptoms using twice-weekly diary records. However, over the same period in the community, there were peaks in asthma emergency visits both at a large local hospital and in state-wide hospitalizations, following both return to school (February) and in late autumn (May) in children of the same age. This study suggests that hRV infections are common throughout the year among children, and differences in virus prevalence alone may not account for peaks in asthma symptoms., (© 2015 Wiley Periodicals, Inc.)

Background: Viruses are frequently associated with acute exacerbations of asthma, but the extent to which they contribute to the level of day-to-day symptom control is less clear., Objective: We sought to explore the relationship between viral infections, host and environmental factors, and respiratory symptoms in children., Methods: Sixty-seven asthmatic children collected samples twice weekly for an average of 10 weeks. These included nasal wash fluid and exhaled breath for PCR-based detection of viral RNA, lung function measurements, and records of medication use and asthma and respiratory symptoms in the previous 3 days. Atopy, mite allergen exposure, and vitamin D levels were also measured. Mixed-model regression analyses were performed., Results: Human rhinoviruses (hRVs) were detected in 25.5% of 1232 nasal samples and 11.5% of breath samples. Non-hRV viruses were detected in less than 3% of samples. hRV in nasal samples was associated with asthma symptoms (cough and phlegm: odds ratio = 2.0; 95% CI = 1.4-2.86, P = .0001; wheeze and chest tightness: odds ratio = 2.34, 95% CI = 1.55-3.52, P < .0001) and with cold symptoms, as reported concurrently with sampling and 3 to 4 days later. No differences were found between the 3 hRV genotypes (hRV-A, hRV-B, and hRV-C) in symptom risk. A history of inhaled corticosteroid use, but not atopic status, mite allergen exposure, or vitamin D levels, modified the association between viruses and asthma symptoms., Conclusion: The detection of nasal hRV was associated with a significantly increased risk of day-to-day asthma symptoms in children. Host, virus genotype, and environmental factors each had only a small or no effect on the relationship of viral infections to asthma symptoms., (Copyright © 2014 American Academy of Allergy, Asthma & Immunology. All rights reserved.)

Unlabelled: Studies that estimate indoor aeroallergen exposure typically measure a pre-selected limited range of allergens. In this study, inhalable aeroallergen particles were quantified using the halogen immunoassay (HIA) to determine the contribution of fungal and non-fungal aeroallergens to total allergen exposure. Bioaerosols from 39 homes of fungal-allergic subjects were sampled using inhalable fraction samplers and immunostained by HIA using resident subject's immunoglobulin E (IgE) to detect allergen-laden particles. Fungal aerosols as well as particles carrying mite, cat, and cockroach allergens were identified and enumerated by HIA. Reservoir dust-mite (Der p 1), cat (Fel d 1), and cockroach (Bla g 1) allergen concentrations were quantified by ELISA. Fungal particles that bound subject's IgE in the HIA were 1.7 (bedroom)- and 1.4 (living room)-fold more concentrated than Der p 1, Fel d 1, and Bla g 1 allergen particles combined. Predominant fungal conidia that bound IgE were derived from common environmental genera including Cladosporium and other fungi that produce amerospores. Airborne mite, cat, and cockroach allergen particle counts were not associated with reservoir concentrations determined by ELISA. This study demonstrates that inhalable fungal aerosols are the predominant aeroallergen sources in Sydney homes and should be considered in future exposure assessments., Practical Implications: Indoor allergen exposure assessment studies have primarily focused on a limited range of allergen sources in samples derived from reservoir dust samples. Using an innovative immunodiagnostic approach, this study demonstrates that fungal bioaerosols are the dominant source of aeroallergen exposure in the domestic environment, providing unique insight into domestic aeroallergen exposure., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Aerosol transmission routes of respiratory viruses have been classified by the WHO on the basis of equilibrium particle size. Droplet transmission is associated with particles sized >5 µm in diameter and airborne transmission is associated with particles sized ≤5 µm in diameter. Current infection control measures for respiratory viruses are directed at preventing droplet transmission, although epidemiological evidence suggests concurrent airborne transmission also occurs. Understanding the size of particles carrying viruses can be used to inform infection control procedures and therefore reduce virus transmission. This study determined the size of particles carrying respiratory viral RNA produced on coughing and breathing by 12 adults and 41 children with symptomatic respiratory infections. A modified six-stage Andersen Sampler collected expelled particles. Each stage was washed to recover samples for viral RNA extraction. Influenza A and B, parainfluenza 1, 2 and 3, respiratory syncytial virus (RSV), human metapneumovirus and human rhinoviruses (hRV) were detected using RT-PCR. On breathing, 58% of participants produced large particles (>5 µm) containing viral RNA and 80% produced small particles (≤5 µm) carrying viral RNA. On coughing, 57% of participants produced large particles containing viral RNA and 82% produced small particles containing viral RNA. Forty five percent of participants produced samples positive for hRV viral RNA and 26% of participants produced samples positive for viral RNA from parainfluenza viruses. This study demonstrates that individuals with symptomatic respiratory viral infections produce both large and small particles carrying viral RNA on coughing and breathing., (© 2013 Wiley Periodicals, Inc.)

Background: The bed is commonly regarded as the main site of house dust mite exposure; however this has not been directly established by continuous measurements. The objective of this study was to determine the pattern of personal exposure to mite aeroallergen over 24 hours., Methods: 12 adults each collected 9 sequential samples (8 during the day, mean 115 mins, and one overnight, mean 514 mins) over 24 hours using a portable air-pump (2L/min) connected to an IOM filter located on the shoulder during the day and on the bed head overnight. Samples were analysed for mite allergen Der p 1 by ELISA. Location and activity were recorded. A mixed model analysis was performed to determine exposure as a function of 14 categories of activity., Results: Personal aeroallergen exposure differed widely over time, both within and between subjects. The highest average exposure (1117 pg/m(3), 95% CI: 289-4314) occurred on public transport and the lowest overnight in bed (45 pg/m(3), 95% CI: 17-17), which contributed only 9.8% (95% CI: 4.4%-15.1%) of total daily exposure. Aeroallergens were not related to bed reservoirs., Conclusion: The study challenges the current paradigm that the bed is the main site of HDM exposure and instead suggests most exposure occurs in association with domestic activity and proximity to other people. Effective mite interventions, designed to improve asthma outcomes, need to first identify and then address the multiple sources of aeroallergen exposure.

Background: Exposure to London Plane Tree (Platanus) bioaerosols in Sydney, Australia has been anecdotally linked to respiratory irritation, rhinitis, and conjunctivitis., Objective: To determine the relationships between Platanus bioaerosol exposure, allergic sensitization, and symptoms., Methods: Sixty-four subjects with self-reported Platanus symptoms were recruited from inner-urban Sydney. Allergic sensitization was determined by skin prick test (SPT) to 13 allergens. Airborne concentrations of Platanus pollen, trichomes, and achene fibers, and other pollen and fungal spores, were measured over the spring and summer of 2006-2007. Subjects' allergic symptoms were monitored concurrently. The Halogen immunoassay (HIA) was used to measure subjects' immunoglobulin E (IgE) reactivity to collected bioaerosols., Results: Platanus pollen constituted 76% of total pollen between July 2006 and April 2007. Airborne concentrations of Platanus pollen peaked from August until October. Non-Platanus pollen peaked from July to December. Elevated concentrations of trichomes and achene fibers occurred from September to December and August to October, respectively. As determined by SPT, 85.9% of subjects were sensitized, 65.6% to any pollen tested, 56.3% to Lolium perenne, and 23.4% to Platanus. Higher mean daily symptom scores were only associated with high counts of non-Platanus pollens. HIA analysis demonstrated IgE binding to Platanus pollen in all Platanus sensitized subjects. Personal nasal air sampling detected airborne trichomes that were capable of being inhaled. Platanus trichomes or achene fibers did not bind IgE from any subject., Conclusions: Platanus bioaerosols exist in high concentrations between August and November in inner-urban Sydney but were not associated with seasonal symptoms. Platanus trichomes are inhaled and may constitute a respiratory irritant., Trial Registration: Clinicaltrials.gov Identifier: NCTXXXXX., (Copyright © 2011 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

The role of allergen exposure in the etiology of allergic sensitization and asthma is complex. Advice on strategies to avoid domestic allergens remains contentious because trials of interventions aimed to prevent asthma or reduce symptoms have often failed to demonstrate benefits. Asthma management guidelines differ widely in their recommendations, while Web-based information often claims benefits associated with products. In this rostrum we argue that although many factors have a role in both the etiology and the exacerbation of asthma, allergen exposure probably remains an important contributor to the manifestations of the disease. Currently, there is no evidence-based framework for effective domestic allergen avoidance interventions to reduce chronic aeroallergen exposure. The development of an effective approach to allergen avoidance requires a better understanding of (a) the physical nature of chronic aeroallergen exposure and methods for measuring and reducing this, (b) the interaction between allergen exposure and innate immune modulators at different disease stages, and (c) markers enabling the identification of individuals who would benefit from this. The strategic risk of overemphasizing other novel mechanisms and approaches to asthma management is that we will prematurely abandon and fail to improve an existing approach that could have a significant impact on the development, progression, and symptoms of the disease., (Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

A sudden increase in the rate of asthma exacerbations has been observed among young children in many countries 2-3 weeks after their return-to-school following the summer holidays. These exacerbations are frequently associated with human rhinovirus (hRV) infections, with possible interactions with allergen sensitisation, allergen exposure and medication use. It was originally proposed that the sudden increase resulted from new strains of respiratory viruses acquired during the holidays spreading rapidly on return to school. While there is compelling evidence implicating hRV in these exacerbations, recent observations on virus transmission, infection patterns and immune responses to both viruses and allergens have led us to propose an additional hypothesis for this increase in exacerbations. We propose that classrooms typically provide persistent exposure to a mixture of airborne viruses, viral proteins, endotoxin, community allergens and other human-derived aerosols - a modern miasma. During the preceding school term, this exposure establishes and maintains a level of immune tolerance and herd immunity, which then declines during the two-month holidays due to lack of such exposure, creating a transitory window of susceptibility to viral infections and asthma. The return to school re-establishes exposure to these aerosols resulting in an acceleration of exacerbations, until the tolerance and herd immunity are re-established. Thus, the peak in return-to-school asthma is more a function of a transitory increase in susceptibility due to a temporary lack of this complex exposure, than it is to novel, locally endemic strains of hRV., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Variation in the observed association between pet ownership and allergic disease may be attributable to selection bias and confounding. The aim of this study was to suggest a method to assess disease-related modification of exposure and second to examine how cat acquisition or dog ownership in early life affects atopy and asthma at 5 years. Information on sociodemographic factors and cat and dog ownership was collected longitudinally in an initially cat-free Australian birth cohort based on children with a family history of asthma. At age 5 years, 516 children were assessed for wheezing, and 488 for sensitisation. Data showed that by age 5 years, 82 children had acquired a cat. Early manifestations of allergic disease did not foreshadow a reduced rate of subsequent acquisition of a cat. Independent risk factors for acquiring a cat were exposure to tobacco smoke at home odds ratio (OR) 1.92 [95% confidence interval (CI) 1.13, 3.26], maternal education < or =12 years OR 1.95 [1.08, 3.51] and dog ownership OR 2.23 [1.23, 4.05]. Cat or dog exposure in the first 5 years was associated with a decreased risk of any allergen sensitisation, OR 0.50 [0.28, 0.88] but no association with wheeze OR 0.96 [0.57, 1.61]. This risk was not affected by age at which the cat was acquired or whether the pet was kept in- or outdoors. In conclusion, cat or dog ownership reduced the risk of subsequent atopy in this high-risk birth cohort. This cannot be explained by disease-related modification of exposure. Public health recommendations on the effect of cat and dog ownership should be based on birth cohort studies where possible selection bias has been taken into account.

OBJECTIVE: Conidia derived from a small number of common fungal genera are widely accepted as the etiological agents responsible for fungal allergic sensitization. The contribution of fungal conidia, spores, airborne hyphae, and subcellular fragments from other uncharacterized fungal genera remains unclear. In this proof-of-concept study, we examined the composition of mycoaerosols that atopic women were exposed and sensitized to in their own indoor environment using the fluorescent halogen immunoassay (fHIA). PATIENTS AND METHODS: Mycoaerosols were collected onto mixed cellulose ester protein binding membranes (PBMs) for 30 minutes with volumetric air sampling pumps. The PBMs were laminated with an adhesive cover slip and indirectly immunostained with individual patient serum IgE using the fHIA. Samples were examined using confocal laser scanning microscopy and immunostained particles were expressed as a percentage of total particles. RESULTS: All air samples contained a broad spectrum of fungal spores, conidia, hyphae, and other fungal particulates. Airborne concentrations varied between individual study participant environments. Positively immunostained conidia belonging to moniliaceous amerospores, Cladosporium, Alternaria, and many unknown species were observed in the majority of air samples. Other fungal genera including Bipolaris, Curvularia, Pithomyces, and Stachybotrys, in addition to, ascospore genera and dematiaceous hyphal fragments released detectable allergen. Twelve percent of all fHIA haloes quantified in the analysis were directed towards fungal particles. No immunostaining was detected to conidia belonging to Epicoccum, Fusarium, and Spegazzinia species. CONCLUSION: In addition to characterized fungal aeroallergens, we observed a wider composition of fungi that bound human IgE. Field surveillance studies that utilize immunodiagnostic techniques such as the fHIA will provide further insight into the diversity of fungi that function as aeroallergen sources in individual study participant environments.

There is a lack of quantitative information about the generation of virus aerosols by infected subjects. The exhaled aerosols generated by coughing, talking, and breathing were sampled in 50 subjects using a novel mask, and analyzed using PCR for nine respiratory viruses. The exhaled samples from a subset of 10 subjects who were PCR positive for rhinovirus were also examined by cell culture for this virus. Of the 50 subjects, among the 33 with symptoms of upper respiratory tract infections, 21 had at least one virus detected by PCR, while amongst the 17 asymptomatic subjects, 4 had a virus detected by PCR. Overall, rhinovirus was detected in 19 subjects, influenza in 4 subjects, parainfluenza in 2 subjects, and human metapneumovirus in 1 subject. Two subjects were co-infected. Of the 25 subjects who had virus-positive nasal mucus, the same virus type was detected in 12 breathing samples, 8 talking samples, and in 2 coughing samples. In the subset of exhaled samples from 10 subjects examined by culture, infective rhinovirus was detected in 2. These data provide further evidence that breathing may be a source of respirable particles carrying infectious virus.

Background: There is uncertainty about the nature of the relationship between mite allergen exposure during infancy and the expression of allergic diseases in childhood., Objective: We sought to explore the relationships between repeated measurements of mite allergen exposure during the first 5 years of life and clinical allergic disease outcomes at age 5 years., Methods: In a birth cohort of 516 at-risk children, 13 bed dust samples were collected between birth and 5 years of age and analyzed for mite allergen. At age 5 years, the presence of mite atopy was assessed based on skin prick test results, and clinical assessments for asthma, eczema, and wheeze were conducted. The association of allergen exposure with each clinical outcome was examined by means of logistic regression, with adjustments for potential confounders., Results: The lowest and highest mite exposure quintiles, expressed as mean allergen concentration averaged over 0 to 5 years, were associated with a lower prevalence of mite atopy and of asthma compared with intermediate levels of exposure. These relationships, when determined by using average allergen concentration over 0 to 18 months, were weaker., Conclusions: This study demonstrates a nonlinear relationship between mite allergen exposure and clinical outcomes in this generally high mite allergen environment.

The systematic avoidance of indoor allergens by modification of houses, furnishings, or hygiene practices has long been advocated to reduce both the incidence of allergic diseases in at-risk infants and exacerbations or symptoms in those previously sensitized with such a disease. However, such advocacy is now under challenge, due to both a lack of evidence of clinical efficacy of avoidance measures and rapidly changing models of disease causation and pathology. This article reviews the current dilemmas in understanding the complexity of allergen sources, disease risks, nature of bioaerosol exposure, and the inadequacies of many available methods.

We have developed a mask sampler for exhaled respiratory viruses. Among a group of 9 patients with cold symptoms who had virus-positive nasal mucus specimens, as analyzed by multiplexed polymerase chain reaction, virus-positive mask samples were obtained after coughing (20 times), talking (20 min), or breathing (20 min) from 6, 5, and 3 patients, respectively.

Background: Sensitization and symptoms of allergic disease are strongly correlated, but little is known about the early clinical precursors of the development of allergen sensitization in childhood. The aim of this study was to identify these predictors, and to examine separately the effect of early sensitization on subsequent wheeze, asthma, rhinitis and eczema., Methods: In the Childhood Asthma Prevention Study, children with a family history of asthma were assessed for allergen sensitization, total serum IgE, wheeze, asthma, eczema and rhinitis at ages 18 months and 5 years. To examine predictors, at 18 months, for subsequent sensitization, children who were non-sensitized at 18 months and had data on sensitization at 5 years were investigated, n=375. To examine the predictors, at age 18 months, of subsequent onset of symptoms, children who did not have wheeze, asthma, eczema or rhinitis at 18 months were followed-up at 5 years, n=177., Results: Among children who were non-sensitized at age 18 months, the presence of eczema [adjusted relative risk (aRR), 1.67, 95% confidence interval (CI) 1.20-2.33], but not wheeze, asthma or rhinitis, was an independent predictor of the onset of sensitization by age 5 years. Among children who were asymptomatic at age 18 months, sensitization to any allergen at 18 months was an independent predictor for the presence of wheeze (aRR 2.41, 95% CI 1.28-4.55), asthma (aRR 4.66, 95% CI 1.88-11.54) and rhinitis (aRR 1.77, 95% CI 1.08-2.90), but not for the development of eczema (aRR 0.78, 95% CI 0.23-2.64) at 5 years., Conclusion: In non-sensitized children, eczema, but not wheeze, asthma or rhinitis is a predictor for subsequent development of sensitization. This suggests that early childhood eczema, rather than wheeze and rhinitis, may promote subsequent allergen sensitization and raises the possibility that early management of eczema may reduce the prevalence of sensitization in children.

We examine the nature of the immune responses to inhaled skin particles and query whether early exposure could play a role in providing protection against the development of allergic disease. Currently, the main hypothesis used to explain environmental modulation of allergic diseases, the 'hygiene hypothesis', is linked exclusively to microbial exposures acting upon the innate immune system. However, many of the exposures sustaining this hypothesis also involve co-exposure to skin flakes from humans or animals. Such skin flakes contain a complex mixture of antigens, glycolipids and small peptides that may induce immune responses. Should these responses prove relevant to the modulation of allergic diseases, it provides new opportunities to better understand the epidemic of allergic disease and to develop new interventions for its prevention.

Background: Carpets are large reservoirs of the dust mite allergen Der p 1. The effect of vacuum cleaning on the distribution of Der p 1 in carpets is poorly understood., Methods: Samples were cut from 7 used household carpets, all over 5 years of age. From each carpet, 10 samples were left untreated, 10 vacuumed with an upright vacuum cleaner, and 10 vacuumed with a canister vacuum cleaner. Each section was then cut into 3 horizontal layers: the top 2mm, the remainder of the carpet pile, and the carpet base. The mass of Der p 1 as a proportion of carpet volume was then determined., Results: The concentrations of Der p 1 in each depth layer varied considerably between the 7 untreated carpets. In the top layer, Der p 1 concentrations were (median; 25th-75th percentiles): 41.9; 28.3-92.6 pg/mm3. For the middle layer they were similar (38.1; 22.4-108.5 pg/mm3), and for the carpet base, higher (212.4; 98.8-456.2 pg/mm3). In most cases, cleaning using either type of vacuum cleaner resulted in no significant reduction in allergen concentration throughout all depth layers. A subset of carpets showed an apparent increase in Der p 1 concentration in one or more layers following vacuum cleaning. In all tests Der p 1 was collected in the vacuum cleaners' filter bags., Conclusions: The depth-distribution of Der p 1 differs widely amongst used carpets. Vacuum cleaning changes the distribution of Der p 1 within such carpets but does not necessarily result in a reduction in the overall content.

Fungal allergens are present in viable and non-viable conidia, hyphae and fungal fragments. It has been shown that large quantities of allergen are released from conidia during germination. We used a gold immunolabelling technique and field emission scanning electron microscopy to examine the allergen release from Alternaria alternata conidia. Immunolabelling was associated with the hyphal tip and amorphous matter associated with the emerging hyphae. Non-specific antibody controls showed no labelling associated with germinating fungi. This suggests that material released from hyphae may be an additional source of fungal allergens.

Exposure to fungi, particularly in water damaged indoor environments, has been thought to exacerbate a number of adverse health effects, ranging from subjective symptoms such as fatigue, cognitive difficulties or memory loss to more definable diseases such as allergy, asthma and hypersensitivity pneumonitis. Understanding the role of fungal exposure in these environments has been limited by methodological difficulties in enumerating and identifying various fungal components in environmental samples. Consequently, data on personal exposure and sensitization to fungal allergens are mainly based on the assessment of a few select and easily identifiable species. The contribution of other airborne spores, hyphae and fungal fragments to exposure and allergic sensitization are poorly characterized. There is increased interest in the role of aerosolized fungal fragments following reports that the combination of hyphal fragments and spore counts improved the association with asthma severity. These fragments are particles derived from any intracellular or extracellular fungal structure and are categorized as either submicron particles or larger fungal fragments. In vitro studies have shown that submicron particles of several fungal species are aerosolized in much higher concentrations (300-500 times) than spores, and that respiratory deposition models suggest that such fragments of Stachybotrys chartarum may be deposited in 230-250 fold higher numbers than spores. The practical implications of these models are yet to be clarified for human exposure assessments and clinical disease. We have developed innovative immunodetection techniques to determine the extent to which larger fungal fragments, including hyphae and fractured conidia, function as aeroallergen sources. These techniques were based on the Halogen Immunoassay (HIA), an immunostaining technique that detects antigens associated with individual airborne particles >1 microm, with human serum immunoglobulin E (IgE). Our studies demonstrated that the numbers of total airborne hyphae were often significantly higher in concentration than conidia of individual allergenic genera. Approximately 25% of all hyphal fragments expressed detectable allergen and the resultant localization of IgE immunostaining was heterogeneous among the hyphae. Furthermore, conidia of ten genera that were previously uncharacterized could be identified as sources of allergens. These findings highlight the contribution of larger fungal fragments as aeroallergen sources and present a new paradigm of fungal exposure. Direct evidence of the associations between fungal fragments and building-related disease is lacking and in order to gain a better understanding, it will be necessary to develop diagnostic reagents and detection methods, particularly for submicron particles. Assays using monoclonal antibodies enable the measurement of individual antigens but interpretation can be confounded by cross-reactivity between fungal species. The recent development of species-specific monoclonal antibodies, used in combination with a fluorescent-confocal HIA technique should, for the first time, enable the speciation of morphologically indiscernible fungal fragments. The application of this novel method will help to characterize the contribution of fungal fragments to adverse health effects due to fungi and provide patient-specific exposure and sensitization profiles.

Background: Early life exposures may be important in the development of asthma and allergic disease., Objective: To test house dust mite (HDM) avoidance and dietary fatty acid modification, implemented throughout the first 5 years of life, as interventions to prevent asthma and allergic disease., Methods: We recruited newborns with a family history of asthma antenatally and randomized them, separately, to HDM avoidance or control and to dietary modification or control. At age 5 years, they were assessed for asthma and eczema and had skin prick tests for atopy., Results: Of 616 children randomized, 516 (84%) were evaluated at age 5 years. The HDM avoidance intervention resulted in a 61% reduction in HDM allergen concentrations (microg/g dust) in the child's bed but no difference in the prevalence of asthma, wheeze, or atopy (P > .1). The prevalence of eczema was higher in the active HDM avoidance group (26% vs 19%; P = .06). The ratio of omega-6 to omega-3 fatty acids in plasma was lower in the active diet group (5.8 vs 7.4; P < .0001). However, the prevalence of asthma, wheezing, eczema, or atopy did not differ between the diet groups (P > .1)., Conclusion: Further research is required to establish whether other interventions can be recommended for the prevention of asthma and allergic disease., Clinical Implications: House dust mite avoidance measures and dietary fatty acid modification, as implemented in this trial during infancy and early childhood, did not prevent the onset of asthma, eczema, or atopy in high-risk children.

Background: Accurate diagnosis of allergy to specific fungal species is confounded by the variability in allergens occurring with different diagnostic systems. We compared the halogen immunoassay (HIA), which uses allergens expressed by freshly germinated spores that are bound to protein binding membranes (PBM), with the commercial Pharmacia UniCap assay (CAP) and with skin prick tests (SPT)., Methods: Serum from 60 subjects was used; 30 were SPT positive and sensitized to at least one of Alternaria alternata or Aspergillus fumigatus and the other 30 were SPT negative to these fungi but known to be sensitized to non-fungal allergens. All sera were analyzed by CAP against A. alternata, A. fumigatus, Cladosporium herbarum and Epicoccum purpurascens. For HIA, spores from reference cultures belonging to these four species were germinated on PBM, laminated and then probed with each serum. Two independent observers using an ordinal ranking system quantified the intensity and occurrence of the resultant immunoglobulin E (IgE) immunostained haloes around spores and this was statistically compared with the results of the two conventional immunodiagnostic techniques., Results: Germinated conidia of each species expressed detectable allergen in the HIA. The agreement between the ordinal rank scores assigned by the pair of observers was very good (k >or= 0.8) and only differed for A. fumigatus (k = 0.66) . Between 3% and 7% of SPT negative sera was identified by HIA to have specific IgE towards A. fumigatus and A. alternata. For all four species tested there were strong correlations between HIA and CAP (P < 0.0001). However the correlation of both HIA and CAP to SPT was weaker for A. alternata (r(s) = 0.44, P < 0.0153) and absent for A. fumigatus., Conclusions: Overall, the HIA is a new immunodiagnostic technique for the detection of sensitization to fungal allergens that correlates significantly with CAP and to a lesser extent with SPT. This may be due to extract variability and system differences. The significance of this derives from the unique ability of the HIA to measure IgE antibodies to the undegraded allergens that are actively secreted by germinating conidia and hyphae. These are the natural agents of exposure to fungi, and as such, are most likely to be relevant to clinical disease.

The identification of collected airborne unicellular fungal conidia and hyphae using nonviable techniques is subjective and an imprecise process. Similarly, to determine whether an individual is allergic to a particular genus requires a separate immunodiagnostic analysis. This study demonstrates the development of a novel double immunostaining halogen assay, which enables (1) the simultaneous identification of collected airborne fungal conidia and hyphae of Aspergillus fumigatus and Penicillium chrysogenum using monoclonal antibodies and (2) the demonstration of patient-specific allergy to the same particles using human serum IgE. The results demonstrate that when conidia were ungerminated the binding of antibodies was homogeneous and localized in close proximity around the entire conidia for both species. However, when conidia were germinated, the proportion expressing antigen increased (P < 0.0001) for both species and the sites of binding of the two antibodies changed with double immunostaining restricted to the hyphal tips for A. fumigatus, in addition to the sites of germination for P. chrysogenum. The described immunoassay has the potential to identify fungal particles in personal environmental air samples, provided species-specific monoclonal antibodies are available, while simultaneously demonstrating allergic sensitization to the same particles by co-staining the samples with the patient's own serum. Such an immunoassay can use those fungi that the patient is actually exposed to and potentially avoids many problems associated with extract variability based on the performance of current diagnostic techniques for fungal allergy.

A double-immunostaining halogen immunoassay was developed to identify aerosolized conidia, hyphae, and fragments of Alternaria alternata by using an anti-Alternaria polyclonal antiserum, while, simultaneously, allergy to these components was concurrently determined by using human immunoglobulin E antibodies.

Airborne fungi are ubiquitous in the environment and human exposure is inevitable. Such fungi differ greatly in their taxonomic, physical, ecological, behavioral, and pathogenic characteristics. Many strategies have evolved to sample, identify and interpret fungal exposure and their choice is determined by the hypotheses involved. While fungi can be sampled directly from surfaces, results do not generally reflect human exposure. For this reason, airborne spores are commonly sampled, by either filtration or impaction, using volumetric air samplers. Identification is commonly performed by either culture on nutrient medium or light microscopy using morphological criteria, although new techniques using DNA probes or characteristic antigens or toxins continue to be developed. Interpretation of such exposure data is both complex and contentious, but while there are numerous recommendations there is no consensus on exposure thresholds. A better understanding of the complex pathogenic roles of fungi and susceptibilities of their hosts will enable refinement of techniques for sampling and interpretation.

Background: More than 100 genera of fungal conidia are currently recognized as sources of allergens. The contribution of other fungal genera plus airborne fungal hyphae and fragmented conidia to allergic diseases is poorly understood., Objective: We sought to investigate the expression of allergens from airborne wild-type fungi using the Halogen immunoassay, which uses allergic serum IgE to immunostain immobilized allergens extracted from individual fungal particles., Methods: Airborne fungi were collected onto mixed cellulose ester protein-binding membranes for 2.5 hours with volumetric air pumps. Collected fungi were incubated overnight in a humid chamber to promote the germination of conidia. The membranes were laminated with an adhesive cover slip and immunostained with an Alternaria species-sensitive serum IgE pool. The samples were examined by means of light microscopy, and positively immunostained fungal particles were classified and counted., Results: All air samples contained fungal hyphae that expressed soluble allergens and were significantly higher in concentration than counts of conidia of individual well-characterized allergenic genera (P < .05). Resultant immunostaining of fungal hyphae was heterogeneous, and approximately 25% of all hyphae expressed detectable allergen compared with nonstained hyphae (P < .05). Fungal conidia of 10 genera that were previously uncharacterized as allergen sources were shown to demonstrate IgE binding to expressed antigens and accounted for 8% of the total airborne conidia count., Conclusions: Our analysis of wild-type fungi collected indoors presents a new paradigm of natural fungal exposure, which, in addition to commonly recognized species, implicates airborne hyphae, fragmented conidia, and the conidia of a much more diverse range of genera as airborne allergens.

Background: Prototype nasal filters were developed to collect inhaled pollen. This study evaluated the efficacy of the filters for prevention of rhinitis symptoms during acute outdoor pollen exposure., Methods: A randomized double-blind design was used. Subjects (n=46) with a history of autumn exacerbation of rhinitis and positive skin test to ragweed, Bermuda and/or Bahia grass wore either active or placebo nasal filters for 2 h in autumn in a park containing these species. Major and Total Symptoms scores were recorded at 0, 30, 60, 90 and 120 min., Results: Subjects wearing active nasal filters had significantly reduced scores, at all time-points compared with placebo group (all P <0.05). Of 14 individual symptoms measured, seven were significantly reduced (number of sneezes, runny nose, itchy nose, sniffles, itchy throat; itchy eyes and watery eyes) and another three showed a trend towards lower severity. The nasal filters also enabled the resolution of existing symptoms. Maximal difference in symptoms was seen immediately after subjects had spent 20 min sitting beside a large patch of ragweed., Conclusion: This is the first clinical trial of a nasal filter. The results suggest it has potential for enhancing rhinitis management during acute allergen exposure.

Background: Simple, inexpensive methods of sampling from allergen reservoirs are necessary for large-scale studies or low-cost householder-operated allergen measurement., Methods: We tested two commercial devices: the Indoor Biotechnologies Mitest Dust Collector and the Drager Bio-Check Allergen Control; two devices of our own design: the Electrostatic Cloth Sampler (ECS) and the Press Tape Sampler (PTS); and a Vacuum Sampler as used in many allergen studies (our Reference Method). Devices were used to collect dust mite allergen samples from 16 domestic carpets. Results were examined for correlations between the sampling methods., Results: With mite allergen concentration expressed as microg/g, the Mitest, the ECS and the PTS correlated with the Reference Method but not with each other. When mite allergen concentration was expressed as microg/m2 the Mitest and the ECS correlated with the Reference Method but the PTS did not. In the high allergen conditions of this study, the Drager Bio-Check did not relate to any methods., Conclusions: The Mitest Dust Collector, the ECS and the PTS show performance consistent with the Reference Method. Many techniques can be used to collect dust mite allergen samples. More investigation is needed to prove any method as superior for estimating allergen exposure.

Background: Two factors thought to influence the risk of asthma are the promoting effect of sensitization to house dust mites and the preventive effect of increased omega-3 fatty acids. Although house dust mite allergen avoidance has been used as a preventive strategy in several trials, the effect of omega-3 fatty acid supplementation in the primary prevention of asthma and allergic disease is not known., Objective: To measure the effects of dietary supplementation with omega-3 fatty acids and house dust mite allergen avoidance in children with a family history of asthma., Methods: A total of 616 children at high risk of asthma were enrolled antenatally in a randomized controlled trial, and 526 children remained in the trial at age 3 years. The outcomes were symptoms of allergic disease and allergen sensitization., Results: There was a significant 10.0% (95% CI, 3.7-16.4) reduction in the prevalence of cough in atopic children in the active diet group ( P=.003; number needed to treat, 10) but a negligible 1.1% (95% CI, -7.1 to 9.5) reduction cough among nonatopic children. There was a 7.2% (95% CI, 10.11-14.3) reduction in sensitization to house dust mite in the active allergen avoidance group ( P=.05; number needed to treat, 14). No significant differences in wheeze were found with either intervention., Conclusion: These results suggest that our interventions, designed to be used in simple public health campaigns, may have a role in preventing the development of allergic sensitization and airways disease in early childhood. This offers the prospect of reducing allergic disease in later life.

Background: Measurement of exposure to the dust mite allergen Der p 1 is important in asthma research and is potentially useful in managing asthma. As no single measure can capture all characteristics of an exposure, it is important to recognize differences in the available methods of measuring exposure to Der p 1., Methods: Fourteen bedrooms and living rooms were sampled using four methods for 1 week. Airborne allergen was sampled by static Institute of Occupational Medicine samplers. Settling dust was collected on Petri dishes and an adhesive-membrane system (A-book). Vacuumed reservoir dust samples were collected from floors at the end of 1 week. Der p 1 was measured in all samples by enzyme-linked immunosorbent assay, except A-books, in which it was measured by Halogen immunoassay., Results: All four methods intercorrelated moderately (r range = 0.40-0.64, P = 0.04), except between allergen in reservoir dust (as microg/m2 and microg/g dust) and settling dust by Petri dishes (P = 0.2). Reservoir allergen, expressed as microg/m2, did not correlate with any measure, except reservoir allergen expressed as microg/g (r = 0.39, P = 0.04). No differences in these associations occurred between bedrooms and living rooms., Conclusions: While the four methods examined correlated moderately, all have practical advantages and difficulties. No method can be considered as ideal for measuring individual exposure. For practicality, use of vacuum cleaner and Petri dish methods are recommended.

Background: In temperate climates, exposure to house dust mite (HDM) allergens is the strongest environmental risk factor for childhood asthma. Environmental modifications to limit exposure have the potential to reduce the prevalence of asthma. The aim of this study was to reduce allergen exposure for children at high risk of developing asthma., Methods: A total of 616 pregnant women were randomized to HDM intervention and control groups. The control group had no special recommendations whereas the intervention group was given allergen impermeable mattress covers and an acaricidal washing detergent for bedding. Children were visited regularly until 18 months of age to have dust collected from their bed., Results: Der p 1 concentrations in the control group increased from 5.20 microg/g at 1 month to 22.18 microg/g at 18 months but remained low in the intervention group, ranging from 3.27 microg/g at 1 month to 6.12 microg/g at 18 months., Conclusions: In a high HDM allergen environment, a combined approach using physical barriers and an acaricidal wash, is effective in reducing HDM allergen concentrations in bedding. However, even with these control measures in place, HDM allergen levels remained high by international standards.

Background: Allergens dispersed by airborne fungal spores play an important but poorly understood role in the underlying cause and exacerbation of asthma. Previous studies suggest that spores of Alternaria and Aspergillus release greater quantities of allergen after germination than before germination. It is unknown whether this is true of other allergenic fungi., Objective: Our purpose was to investigate the release of allergen from a range of individual fungal spores before and after germination., Methods: Allergen expression from spores of Alternaria alternata, Cladosporium herbarum, Aspergillus fumigatus, Botrytis cinerea, Epicoccum nigrum, Exserohilum rostratum, Penicillium chrysogenum, Stemphylium botryosum, Curvularia lunata, Trichoderma viride, and Bipolaris spicifera was examined by halogen immunoassays through the use of pooled serum IgE from patients allergic to fungus. Spores were deposited onto protein-binding membranes direct from culture. To germinate spores, samples were incubated in high humidity at room temperature for 48 hours. Ungerminated and germinated samples were then laminated with an adhesive film and immunostained by the halogen assay. The samples were examined by light microscopy, and positive counts (haloed particles) were expressed as percentages of total spores., Results: For 9 of 11 species, between 5.7% and 92% of spores released allergen before germination. Spores of Penicillium and Trichoderma did not release detectable allergen. After germination, all spores that germinated had allergen elution from their hyphae. Eight of 11 species showed a significant increase (P <.05) in the percentage of spores eluting detectable allergen. Localization of allergen along the hyphae varied with species, such that some eluted allergen mainly from hyphal tips and septal junctions whereas others eluted allergen along the entire length., Conclusions: Increased elution of allergen after germination might be a common feature of many species of allergenic fungi. Although allergens from both spores and hyphae were recognized by human IgE, the extent to which human exposure occurs to allergens eluted from inhaled spores or from hyphae that germinate after deposition in the respiratory tract remains to be explored. The patterns of allergen expression might affect the clinical response to such exposure.

Background: Observational studies have linked house dust mite (HDM) exposure and dietary fatty acid intake with asthma in childhood. However, definitive evidence of their role in the etiology of asthma requires a randomized controlled trial., Objective: We hypothesized that the incidence of asthma and allergy in high-risk children would be reduced by avoidance of HDM allergens, supplementation with omega-3 fatty acids, or the combination of these strategies. We present the results of an interim analysis reporting outcomes assessed at 18 months., Methods: A total of 616 pregnant women were randomized to an HDM avoidance intervention, comprising the use of impermeable mattress covers and an acaricide or control and the use of an oil supplement, margarines, and cooking oils containing high levels of omega-3 fatty acids or control. Atopic status was measured by skin prick testing. Symptoms, diagnoses, and medication histories were elicited by means of parental interviews., Results: The diet intervention resulted in a 9.8% absolute reduction (95% CI, 1.5-18.1; P =.02) in the prevalence of any wheeze and a 7.8% absolute reduction (95% CI, 0.5-15.1, P =.04) in prevalence of wheeze of >1 week, but it had no effect on serum IgE, atopy, or doctors' diagnosis of asthma. The HDM avoidance intervention did not affect these outcomes but was associated with a lower use of oral steroids., Conclusion: Increasing dietary omega-3 fatty acids might have a beneficial effect on the prevalence of wheeze during the first 18 months of life. Follow-up to age 5 years, when the effect of the interventions on asthma risk will be assessed, is underway.

Background: The fungus Alternaria alternata contains potent allergens, and sensitization to these allergens is associated with a high risk of respiratory disease. The influence of genetic regulation on sensitization to Alternaria is unknown., Objective: To determine the influence of genetic factors on IgE responses to specific allergens of Alternaria., Methods: The concordance of skin prick test (SPT), radioallergosorbent test (RAST) and IgE-binding profiles of sera were examined from a large cohort of monozygotic and dizygotic twins., Results: Casewise concordance for a positive SPT response was monozygous (MZ) 66%: dizygous (DZ) 40% (P = 0.002). Logistic regression confirmed that casewise concordance was significantly stronger between MZ than DZ pairs. Immunoblotting against an Alternaria extract revealed 19 allergenic bands. The differences in concordance between the different bands were not significant for either the MZ (P = 0.97) or DZ (P = 0.84) groups. The pooled MZ : DZ difference in concordance was just significant (P = 0.049), suggesting an overall genetic effect on the response to Alternaria. This was reinforced by the comparison of the MZ and DZ correlations for total number of bands recognized (MZ r = 0.65; DZ r = 0.37, P = 0.015). Overall, there was a moderate correlation between the individual SPT weal size and RAST score (r(2) = 0.41) and a substantial correlation between the number of immunoblotted bands and RAST scores (r(2) = 0.79)., Conclusion: There is a strong genetic influence on IgE response to the mixture of Alternaria allergens and a lesser effect on IgE response to individual allergens.

Background: Although allergy to latex is a well-characterized phenomenon, some hospitals continue to provide staff with powdered latex gloves as an option to low- or non-powdered gloves., Objective: We aimed to measure the extent to which inhalation of latex particles could be reduced by the use of protective masks or by replacing powdered latex gloves with non-powdered latex gloves., Methods: Twenty healthcare workers in a hospital setting wore nasal air samplers (NAS) and Institute of Occupational Medicine (IOM) samplers for four 20-min periods. Subjects wore powdered gloves, non-powdered gloves and no gloves during three sampling periods, and in the fourth, subjects applied an aerosol barrier face-mask or a particulate face-mask (N95) while wearing powdered gloves. All samples were stained for particles bearing Hev b 5 allergen by the Halogen assay., Results: All subjects inhaled Hev b 5 bearing particles in all sampling periods. IOM samplers collected particles at 70% of the rate of NAS. The number of particles inhaled while wearing powdered gloves was 23.8-fold higher than when not wearing gloves and 9.7-fold higher than when wearing non-powdered latex gloves (P < 0.0001). Wearing an aerosol barrier mask did not significantly reduce the number of particles inhaled (P = 0.108), while use of particulate masks significantly reduced the number of particles inhaled by 17.4-fold (P = 0.003)., Conclusions: Use of non-powdered gloves is the most effective method of reducing occupational aeroallergen exposure to latex arising from gloves. However, secondary protection using particulate masks is a valid alternative, and may be helpful for preventing respiratory sensitization.

Background: Assessment of personal exposure to dust mite allergen has relied on proxy measures. Only recently has a means to directly measure inhaled allergen particle number become available (the intra-nasal air sampler)., Objective: To quantify inspired dust mite group 1 and group 2 allergen-bearing particles in bed in undisturbed conditions prior to sleep by nasal air sampling and to investigate the relationship between inhaled particles and reservoir allergen levels., Methods: Twelve volunteers wore nasal samplers in bed for 6 evenings, nose-breathing in undisturbed conditions. Allergen-bearing particles ('halos') were detected by immunostaining for Der p 1, Der p 2, or Der p 1 and Der p 2 together, and counted by light microscopy. Count data were square root transformed for analysis of variance. Mattress dust samples were assayed for Der p 1 and Der p 2 concentrations., Results: Square root detransformed mean particle counts per 30-min sample were: Der p 1, 4.22; Der p 2, 5.9; Der p 1 + Der p 2, 4.87; and for all samples, 5.01, with no difference between the groups. With replicate samples, halo number correlated significantly with mattress allergen concentrations (Der p 1 r = 0.80, P < 0.01; Der p 2 r = 0.68, P < 0.02)., Conclusion: Nasal air sampling can be used to quantify nocturnal Der p exposure in undisturbed conditions in an area with moderate exposure to mite allergen and can provide a direct measure of inhaled mite allergen. The choice of either Der p 1 or Der p 2 is appropriate for this purpose.

Background: IgE-mediated responses to natural rubber latex allergens have become a major health problem among recognized risk groups., Objective: The purpose of this investigation was to measure the amounts of Hevea brasiliensis latex allergen (Hev b 1) inhaled and deposited on surfaces when latex or vinyl gloves were worn and compare the results with the conventional measures (breathing zone samplers) of occupational exposure., Methods: Hev b 1 exposure was measured by nasal sampling and breathing zone sampling. Latex allergen exposure was generated by having each subject don a pair of powdered latex examination gloves and continuing his or her normal daily activity for 30 minutes. By means of adhesive tape, surface dust samples were collected from the surfaces of gloves, the subject's hands, and work areas. Sampling was performed with subjects wearing no gloves, subjects wearing powdered vinyl gloves, subjects wearing powdered latex gloves, and nearby colleagues wearing latex gloves. All samples were assayed through use of the HALOgen assay (Inhalix, Sydney, Australia) with a Hev b 1-specific mAb. Particles transporting latex allergen were identified by a surrounding immunostain halo, and these were quantified and reported as total numbers of particles inhaled, airborne, or found on surface areas evaluated., Results: Study subjects inhaled 26 times more allergen when powdered latex gloves were worn than under the "no glove" and powdered vinyl glove conditions. During the same period, Hev b 1 particle levels measured in the ambient air through use of the breathing zone sampler increased by 24-fold. The median numbers of particles carrying Hev b 1 allergen per square centimeter on the surface of the hands after the wearing of latex and vinyl gloves were 1964 and 5, respectively. Latex allergen was physically associated both with cornstarch granules and with larger dust particles having a darker, more irregular appearance., Conclusion: In a laboratory where gloves are worn for protection, the use of latex gloves resulted in a 26-fold increase in inhaled latex allergen over background levels measured while vinyl gloves were worn as controls. Low levels of latex exposure also occurred when vinyl gloves or no gloves were worn; the reasons for this are under investigation.