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Endotoxin may affect the development of allergic disease in childhood but little is known about endotoxin variation within homes. We sought to determine endotoxin concentration agreement within homes when five locations were each sampled twice 5 months apart. Endotoxin was measured using the recombinant Limulus factor C assay in dust samples from 585 homes of children enrolled in a prospective study and again in 335 homes 5 months later. The five locations sampled in each home were the child's bedroom floor, child's bed, mother's bedroom floor, mother's bed and living room floor. Concentrations of 4 allergens (Can f 1, Fel d 1, Der f 1 and Bla g 2) were also measured from the child's bedroom floor. In pair-wise comparisons, endotoxin concentrations in all locations within each home were significantly different from all other locations (p < 0.001) except for the child's and mother's bedroom floors (p = 0.272). Spearman correlations between endotoxin concentrations from the different locations were all statistically significant (p < 0.05) but of modest magnitude (r = 0.24-0.54). Similarly, correlations at each site over the 5 month observation interval were statistically significant but modest (r = 0.17-0.44). Pets and season of the year did not affect correlations, although correlations were lower if the floor was not carpeted. Endotoxin concentrations at all locations were minimally correlated with allergen concentrations in both negative and positive directions (r = -0.12 to 0.12). We conclude that a single measurement of endotoxin from a home dust sample provides an imprecise estimate of dust endotoxin concentrations in other locations within the home and over a relatively short observation interval.

Background: Pregnancy alters the function of many body systems, including the immune system. However, little is known regarding the effect of pregnancy on maternal IgE levels or atopy., Objective: To determine whether pregnancy consistently influences serum levels of total or allergen specific IgE., Methods: Blood samples were obtained from 764 women during the third trimester of pregnancy and 1 month post partum. A third sample was obtained from 106 of these women 1 year post partum. Samples were analyzed for total and specific IgE to 8 regionally common allergens using a commercially available system. Sensitization was defined as an allergen specific IgE level of 0.35 kU of allergen per liter or higher to any allergen., Results: Total IgE increased significantly post partum, both at 1 month (40.36 vs 35.37 IU/mL intrapartum; P = .001) and at 1 year (44.97 vs 37.00 IU/mL intrapartum; P = .005). Allergen specific IgE decreased significantly at 1 month for cat, dog, ragweed, timothy grass, and egg (P = .001 to P = .02) but not for dust mite, cockroach, or Alternaria (P = .15 to P = .90). Similar patterns of change in total and specific IgE were seen at 1 year. However, on average, only 3.5% of participants changed sensitization status to the individual allergens studied during the 1 year of observation., Conclusions: Compared with intrapartum levels, total IgE levels increased significantly at 1 month and 1 year post partum. Conversely, at the same time points, IgE levels specific for common allergens significantly declined to most but not all allergens. Few women changed their sensitization status over 1 year.

Background: The hygiene hypothesis suggests that early infections might protect against later allergic sensitization., Objective: The purpose of this study was to determine whether fevers before age 1 year were associated with allergic sensitization at age 6 to 7 years., Methods: Eight hundred thirty-five children from suburban Detroit, Michigan, were enrolled at birth. Clinic records from their first year were abstracted for episodes of fever, antibiotic use, and respiratory infections. Fever was defined as a rectal temperature of 38.3 degrees C (101 degrees F) or greater or its equivalent measured at another site. At age 6 to 7 years, 441 children underwent allergy testing. The primary outcome measures were atopy (>/=1 positive skin prick test result), seroatopy (>/=1 positive allergen-specific IgE level), and allergic sensitization (either seroatopy or atopy)., Results: By age 1 year, 207 (46.9%) of the 441 participants had a documented fever. Among children with 0, 1, or 2 or more fevers in the first year, 33.3%, 31.3%, and 26.0% demonstrated atopy at age 6 to 7 years, respectively (P =.504); 43.4%, 39.7%, and 25.0% had seroatopy, respectively (P =.032); and 50.0%, 46.7%, and 31.3% had allergic sensitization, respectively (P =.028). After adjusting for potential confounders, each febrile episode in the first year was associated with reduced odds for allergic sensitization (adjusted odds ratio, 0.69; 95% CI, 0.47-1.00). Febrile upper respiratory tract infections, in particular, were associated with lower odds of allergic sensitization (adjusted odds ratio, 0.55; 95% CI, 0.31-0.97) per episode., Conclusion: This study provides direct support for the hygiene hypothesis because children with fevers before age 1 year were less likely to demonstrate allergic sensitivity at age 6 to 7 years.

Background: Indoor dust mite and cat allergens have been related to the risk of atopic conditions. If allergen levels are influenced by modifiable residential characteristics, potential interventions to prevent disease could be deployed., Objective: To evaluate relationships between allergen concentrations in air and dust samples and selected house and household characteristics using a large prospective study with multiple sequential allergen measurements from each residence., Methods: Fel d 1, Der f 1, and Der p 1 were measured in paired air and dust samples collected at intervals throughout 4 years in suburban homes. House and household characteristics were examined for relationships to allergen concentrations in both univariate and multiple variate analyses., Results: The relationships between house and household characteristics and allergen concentrations in both air and dust were complex. When the housing variables were considered in multiple variate analysis, concentrations of Der f 1 in dust increased with increasing number of residents and relative humidity and declined when forced air heating was used. Dust concentrations of Der p 1 were lower in new homes and during forced air heating use but higher with higher relative humidity and in the presence of dogs. The presence of cats was the dominant determinant of Fel d 1 in both air and dust, but when homes without cats were analyzed separately, dust levels of Fel d 1 were inversely related with relative humidity., Conclusions: Air and dust concentrations of Der p 1 and Der f 1 were positively related to relative humidity and the size of the family. Fel d 1 was positively related to the presence of cats. The relationship of other house or household characteristics was inconsistent but different for Der f 1 and Der p 1.

Background: Several studies have suggested that exposure to house-dust mite (HDM) allergen in infancy increases the risk of developing asthma., Objective: To determine whether exposure to higher levels of dust mite in infants increased the risk of developing bronchial hyperresponsiveness (BHR) or physician-diagnosed asthma by age 6 to 7 years., Methods: A health maintenance organization-based cohort of 97 middle class suburban children born from 1987 to 1989 with a high cord blood immunoglobulin E, defined as > or = 0.56 IU/mL, was followed as a part of the Childhood Allergy Study. During the first 2 years of life, monthly bedroom dust samples were collected and analyzed for Der f 1 and Der p 1. Between 6 and 7 years of age, 64 of the original cohort answered a questionnaire used to determine the presence of physician-diagnosed asthma, underwent clinical examination, skin prick testing, and methacholine inhalation challenge. Mann-Whitney tests were used to compare Der f 1 and Der p 1 levels in homes of children with and without BHR, and those with and without physician-diagnosed asthma., Results: In all, 1,421 dust samples were collected and assayed. No significant differences were seen in either the mean, maximum, or minimum dust mite allergen levels in homes of children with versus without BHR, or children with versus without asthma. However, sensitization to HDM was associated with physician-diagnosed asthma (P < 0.05)., Conclusions: When compared with other studies, we were able to more accurately estimate the level of dust mite allergen exposure through repeated sampling over a relatively long period, incorporating seasonal variations. Although HDM sensitization and asthma were concurrently related, we were unable to find any relationship between level of HDM allergen exposure in children's bedrooms in early childhood and development of BHR or physician-diagnosed asthma by age 6 to 7 years.

Context: Childhood asthma is strongly associated with allergic sensitization. Studies have suggested that animal exposure during infancy reduces subsequent allergic sensitization., Objective: To evaluate the relationship between dog and cat exposure in the first year of life and allergic sensitization at 6 to 7 years of age., Design, Setting, and Subjects: Prospective birth cohort study of healthy, full-term infants enrolled in a health maintenance organization in suburban Detroit, Mich, who were born between April 15, 1987, and August 31, 1989, and followed up yearly to a mean age of 6.7 years. Of 835 children initially in the study at birth, 474 (57%) completed follow-up evaluations at age 6 to 7 years., Main Outcome Measures: Atopy, defined as any skin prick test positivity to 6 common aeroallergens (dust mites [Dermatophagoides farinae, D pteronyssinus], dog, cat, short ragweed [Ambrosia artemisiifolia], and blue grass [Poa pratensis]); seroatopy, defined as any positive allergen-specific IgE test result for the same 6 allergens or for Alternaria species., Results: The prevalence of any skin prick test positivity (atopy) at age 6 to 7 years was 33.6% with no dog or cat exposure in the first year of life, 34.3% with exposure to 1 dog or cat, and 15.4% with exposure to 2 or more dogs or cats (P =.005). The prevalence of any positive allergen-specific IgE test result (seroatopy) was 38.5% with no dog or cat exposure, 41.2% with exposure to 1 dog or cat, and 17.9% with exposure to 2 or more dogs or cats (P =.003). After adjustment for cord serum IgE concentration, sex, older siblings, parental smoking, parental asthma, bedroom dust mite allergen levels at 2 years, and current dog and cat ownership, exposure to 2 or more dogs or cats in the first year of life was associated with a significantly lower risk of atopy (adjusted odds ratio, 0.23; 95% confidence interval, 0.09-0.60) and seroatopy (adjusted odds ratio, 0.33; 95% confidence interval, 0.13-0.83)., Conclusion: Exposure to 2 or more dogs or cats in the first year of life may reduce subsequent risk of allergic sensitization to multiple allergens during childhood.

The accurate diagnosis of hypersensitivity to natural rubber latex is the initial step in the effective management of individuals with latex allergy and in ensuring the quality of epidemiologic studies. The diagnostic algorithm used in the evaluation of an individual with suspected latex allergy begins with a comprehensive clinical history during which risk factors (atopy, food allergies, hand dermatitis) and temporal relationships between symptoms and natural rubber product exposure are identified. If type IV hypersensitivity is suspected because of the delayed nature (hours to days) and confinement of symptoms to the skin-latex product contact areas, patch testing can be conducted to confirm the presence of activated T cells with specificity for rubber chemicals. If type I hypersensitivity is suspected because of ocular, upper and lower airway, and/or systemic symptoms that have rapid onset (minutes) after a definable latex exposure, a confirmatory skin or blood test for IgE antibody may be conducted to verify a state of sensitization within the individual. The definitive diagnosis would then be made only after consideration of the individual's clinical history and confirmatory in vivo and/or in vitro laboratory test results. If discordance remains between highly convincing latex-associated symptoms as identified in the history and repetitively negative confirmatory IgE antibody test results, then one of several types of in vivo provocation tests may be performed for adjudication. This overview examines the current state of the art in both in vivo and in vitro diagnostic methods for latex-specific IgE antibody detection in skin and blood. The performance, advantages, and limitations of each diagnostic method are compared.

While serum immunoglobulin E (IgE) concentration has been shown to be related to allergic disease, there have been few studies of the natural history of IgE development in young children. This study compared total and allergen-specific serum IgE concentrations, by gender, from birth through 4 years of age using a population-based cohort of normal children followed from 1987 to 1993. Subjects were enrolled from a geographically defined area through membership in a large health maintenance organization, and they resided in the northern suburbs of Detroit, Michigan. Total IgE concentrations were measured at birth and at 2 and 4 years of age. Specific IgE concentrations to selected common inhalant allergens (dust mite (Dematophagoides farinae), cat, ragweed (Ambrosia artemisiifolia), and timothy grass (Pheleum pratense)) were measured at 2 and 4 years of age. Total IgE increased with age from birth to 4 years for boys and girls, and was higher in boys at 2 and 4 years of age. Girls demonstrated significant increases in IgE to mite and cat and decreases in IgE to ragweed and timothy from 2 to 4 years of age, whereas there was little change for boys except an increase in IgE to ragweed. Differences in IgE development between young boys and girls may partially account for the higher prevalence of asthma in boys than in girls.