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31-03-2010 | Respiratory | Article

Childhood asthma and sensitization risk linked to specific allergens


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MedWire News: There are specific associations between exposure to elevated levels of certain allergens in infancy and the development of allergic sensitization and asthma in later childhood, results from a Canadian study show.

Chris Carlsten (University of British Columbia, Vancouver) and team found that exposure to elevated levels of house dust mite (HDM) allergens in early childhood was associated with an increased risk for allergic sensitization, but not asthma, while the opposite was true for exposure to elevated levels of dog allergens.

Writing in the journal Pediatric Allergy and Immunology, the researchers explain that previous studies investigating the risk for allergic sensitization and asthma associated with childhood exposure to HDM, cat, and dog allergens have produced conflicting results.

To investigate further, the team studied data on 380 children who were followed-up for the first 7 years of life. All the children had at least one first-degree relative with asthma, or two first-degree relatives with other allergic diseases, such as atopic dermatitis, seasonal or perennial allergic rhinitis, or food allergy.

Dust samples from the children’s homes were analyzed for HDM, cat, and dog allergen levels at several time points during the first and seventh years of life.

At the age of 7 years, 71 children had been diagnosed with asthma and 167 were atopic, as indicated by a positive skin prick test result to at least one allergen.

After accounting for factors such as maternal smoking, breastfeeding, daycare attendance, and infection with respiratory viruses, the researchers found that exposure to elevated levels of HDM allergens (at least 2 µg/gm) in household dust in the first year of life was associated with an increased risk for allergic sensitization (odds ratio [OR]=4.18), but not asthma, at the age of 7 years compared with exposure to lower levels of HDM allergens.

In contrast, exposure to higher levels of dog allergens (more than 2 µg/gm) in the first year of life was associated with increased risk for asthma (OR=1.27), but not allergic sensitization, at the age of 7 years compared with lower levels of exposure.

Exposure to higher levels of cat allergen in the first year of life was not associated with sensitization or asthma at the age of 7 years.

Carlsten and team conclude: “In this high-risk cohort, we found allergen-specific associations of exposure with sensitization and with asthma.”

They add: “Although based on modest sample size, our findings add useful data regarding the complex relationship between allergen exposure and clinical end-points.”

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Mark Cowen

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