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Background: The "old friends" hypothesis posits that reduced exposure to previously ubiquitous microorganisms is one factor involved in the increased rates of allergic diseases. Cytomegalovirus (CMV) may be one of the "old friends" hypothesized to help prevent allergic diseases. We sought to elucidate whether early‐life CMV infection is associated with childhood atopy via perturbations of the gut microbiota. Methods: Participants were recruited from a population‐based birth cohort (CHILD study) and followed prospectively until age 5 years in four Canadian cities. A total of 928 participants provided stool microbiome data, urine for CMV testing, skin prick tests, and questionnaire‐based detailed environmental exposures. Cytomegalovirus infection was assessed in the first year of life while the main outcome was defined by persistent sensitization to any allergen at ages 1, 3, and 5 years. Results: Early CMV infection was associated with increased beta and decreased alpha diversity of the gut microbiota. Both changes in diversity measures and early CMV infection were associated with persistent allergic sensitization at age 5 years (aOR = 2.08; 95% CI: 1, 4.33). Mediation analysis demonstrated that perturbation of gut microbial composition explains 30% of the association. Conclusions: Early‐life CMV infection is associated with an alteration in the intestinal microbiota, which mediates the effect of the infection on childhood atopy. This work indicates that preventing CMV infection would not put children at increased risk of developing atopy. Rather, a CMV vaccine, in addition to preventing CMV‐associated morbidity and mortality, might reduce the risk of childhood allergic diseases. [ABSTRACT FROM AUTHOR]

Background: Polyunsaturated fatty acids (PUFAs) may influence immune development. We examined the association of PUFAs in human milk with food sensitization and atopic dermatitis among breastfed infants. Methods: In a selected subgroup of 1109 mother‐infant dyads from the CHILD Cohort Study, human milk was analyzed by gas‐liquid chromatography to quantify PUFAs including arachidonic acid (ARA) and docosahexaenoic acid (DHA). At 1 year of age, food sensitization was determined by skin‐prick testing for egg, peanut, cow's milk, and soybean, and atopic dermatitis was diagnosed by pediatricians. Logistic regression analyses controlled for breastfeeding exclusivity, family history of atopy, and other potential confounders. Results: Overall, 184 infants (17%) were sensitized to one or more food allergens and 160 (14%) had atopic dermatitis. Sex‐specific associations were observed between these conditions and milk PUFAs. Girls receiving human milk with lower proportions of DHA had lower odds of food sensitization (aOR 0.35; 95% CI 0.12, 0.99 for lowest vs highest quintile), and a clear dose‐dependent association was observed for the ARA/DHA ratio (aOR 2.98; 95% CI 1.10, 8.06 for lowest vs highest quintile). These associations were not seen in boys. Similar sex‐specific tendencies were observed for atopic dermatitis. Conclusions: Human milk PUFA proportions and their ratios are associated with infant atopic conditions in a sex‐specific manner. In female infants, a higher ratio of ARA/DHA may reduce the risk of food sensitization and atopic dermatitis. Further research is needed to determine the underlying mechanisms and clinical relevance of this sex‐specific association. [ABSTRACT FROM AUTHOR]

Background: Persisting atopic dermatitis (AD) is known to be associated with more serious allergic diseases at later ages; however, making an accurate diagnosis during infancy is challenging. We assessed the diagnostic performance of questionnaire-based AD measures with criteria-based in-person clinical assessments at age 1 year and evaluated the ability of these diagnostic methods to predict asthma, allergic rhinitis and food allergies at age 5 years.Methods: Data relate to 3014 children participating in the Canadian Healthy Infant Longitudinal Development (CHILD) Study who were directly observed in a clinical assessment by an experienced healthcare professional using the UK Working Party criteria. The majority (2221; 73.7%) of these children also provided multiple other methods of AD ascertainment: a parent reporting a characteristic rash on a questionnaire, a parent reporting the diagnosis provided by an external physician and a combination of these two reports.Results: Relative to the direct clinical assessment, the area under the Receiver Operating Characteristic curve for a parental report of a characteristic rash, reported physician diagnosis and a combination of both were, respectively, 0.60, 0.69 and 0.70. The strongest predictor of asthma at 5 years was AD determined by criteria-based in-person clinical assessment followed by the combination of parental and physician report.Conclusions: These findings suggest that questionnaire data cannot accurately substitute for assessment by experienced healthcare professionals using validated criteria for diagnosis of atopic dermatitis. Combining the parental report with diagnosis by a family physician might sometimes be appropriate (eg to avoid costs of a clinical assessment). [ABSTRACT FROM AUTHOR]

Background The effect of infant feeding practices on the development of food allergy remains controversial. We examined the relationship between timing and patterns of food introduction and sensitization to foods at age 1 year in the Canadian Healthy Infant Longitudinal Development ( CHILD) birth cohort study. Methods Nutrition questionnaire data prospectively collected at age 3, 6, 12, 18, and 24 months were used to determine timing of introduction of cow's milk products, egg, and peanut. At age 1 year, infants underwent skin prick testing to cow's milk, egg white, and peanut. Logistic regression models were fitted to assess the impact of timing of food exposures on sensitization outcomes, and latent class analysis was used to study patterns of food introduction within the cohort. Results Among 2124 children with sufficient data, delaying introduction of cow's milk products, egg, and peanut beyond the first year of life significantly increased the odds of sensitization to that food (cow's milk adj OR 3.69, 95% CI 1.37-9.08; egg adj OR 1.89, 95% CI 1.25-2.80; peanut adj OR 1.76, 95% CI 1.07-3.01). Latent class analysis produced a three-class model: early, usual, and delayed introduction. A pattern of delayed introduction, characterized by avoidance of egg and peanut during the first year of life, increased the odds of sensitization to any of the three tested foods (adj OR 1.78, 95% CI 1.26-2.49). Conclusions Avoidance of potentially allergenic foods during the first year of life significantly increased the odds of sensitization to the corresponding foods. [ABSTRACT FROM AUTHOR]

Background: The influence of breast-feeding on the risk of developing atopy and asthma remains controversial. Objective: To examine asthma and atopy outcomes by sex, reported specific parental history of atopy, and breast-feeding. Methods: In a birth cohort, we examined childhood asthma and atopy (positive skin prick tests) by sex and breast-feeding in relation to maternal and paternal atopy. Interactions were explored in logistic regression models. Results: For boys, breast-feeding (odds ratio [OR], 1.63; 95% CI, 0.93-2.87; P = .09) and maternal atopy (OR, 1.95; 95% CI, 0.93-4.08; P = .08) were each associated with atopy at age 13 years. Breast-feeding increased the risk for atopy among boys with paternal atopy (OR, 7.39; 95% CI, 2.21-24.66) compared with non–breast-fed boys with paternal atopy, but did not significantly further increase risk among subjects with maternal atopy. For girls, breast-feeding (OR, 0.74; 95% CI, 0.41-1.31) and maternal and paternal atopy were not independent risk factors for atopy at age 13 years. However, breast-feeding increased the risk for atopy in girls with maternal atopy (OR, 3.13; 95% CI, 1.20-8.14) compared with non–breast-fed girls with maternal atopy. There was no such effect among subjects with paternal atopy. Results for the outcome of asthma followed a similar pattern. Conclusion: The influence of breast-feeding on development of atopy and asthma differs by sex and by maternal and paternal atopy, and is most significant among subjects at lower baseline risk. Clinical implications: Analyses of environmental risk factors for asthma and atopy should be stratified by specific parental atopy and sex. [Copyright &y& Elsevier]

Background: Exposure to cats and dogs during childhood has been linked to a lower risk of developing allergies. It remains unclear whether this is due to selective avoidance of pets by families with a history of allergies. The effects of pet ownership in adulthood are unknown. Objectives: We sought to assess the association between cat and dog ownership in childhood and early adulthood and the development of atopy in a population-based birth cohort of 1037 subjects. Methods: Ownership of cats or dogs between birth and age 9 years and between the ages of 18 and 32 years was reported. Skin prick tests to common allergens were performed at 13 and 32 years. Results: There was no evidence that families with a history of atopy avoided owning pets. There were significant cat-by-dog interactions for the development of atopy in both childhood and adulthood. Children who had owned both a cat and a dog were less likely to be atopic at age 13 years. Living with only one of these animals was not protective against atopy. Among those who were not atopic by age 13 years, having both a cat and a dog in adulthood was associated with a lower risk of new atopy by age 32 years. This association was only significant among those with a parental history of atopy. These effects were independent of a range of potential confounding factors. Conclusions: There is a synergistic interaction between cat and dog exposure that is associated with a lower risk of developing atopy in childhood and young adulthood. [Copyright &y& Elsevier]