Children with highest exposure to allergens and bacteria during first year of life were least likely to have wheeze and allergic sensitization

The Urban Environment and Childhood Asthma study examined a birth cohort at high risk for asthma (n = 560) in Baltimore, Boston, New York, and St Louis.

Cumulative allergen exposure over the first 3 years was associated with allergic sensitization, and sensitization at age 3 years was related to recurrent wheeze. Reduced exposure to house dust bacterial content in the first year was associated with higher risk of atopy and atopic wheeze.
In contrast, first-year exposure to cockroach, mouse, and cat allergens was negatively associated with recurrent wheeze (odds ratio, 0.60, 0.65, and 0.75, respectively). Exposure to high levels of both allergens and bacteria (Firmicutes and Bacteriodetes) in the first year of life was associated with lower risk of atopy or wheeze.

Concomitant exposure to high levels of certain allergens and bacteria in early life might be beneficial. These findings suggest new preventive strategies for wheezing and allergic diseases.


Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children. Susan V. Lynch et al. Journal of Allergy and Clinical Immunology
Volume 134, Issue 3, Pages 593–601.e12, September 2014.

Image source:, public domain.

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