Allergen avoidance in the primary prevention of asthma

Purpose of review: Six primary prevention studies trialing environmental modifications to reduce asthma in children have published results of clinical outcomes. All are still in progress. Recent findings: In the Isle of Wight study, mite and food avoidance were evaluated to age 9 months. At 8 years, children in the active group had less current wheeze, wheeze with bronchial hyperresponsiveness and atopy (P ≤ 0.05). The Canadian Primary Prevention Study examined avoidance of inhalant and food allergens. At 1 year there was a reduction in probable asthma and rhinitis in the active group. The Study on the Prevention of Allergy in Children in Europe tested avoidance of inhalant and food allergens. At 1 year there was less atopy and sensitization to mites in the active group. In the Childhood Asthma Prevention Study both mite avoidance and a dietary supplement of omega 3 fatty acids were analysed in a factorial design. At age 18 months, children in the dietary intervention group had significantly less wheeze. Eczema was more common amongst children using the mite avoidance measures. The Prevention and Incidence of Asthma and Mite Allergy Study is a placebo-controlled study of mite avoidance. At 2 years, there was a small reduction in nocturnal cough without a cold in the active group. The Manchester Asthma and Allergy Study included stringent environmental control. At 1 year prescribed medication for wheeze and wheeze with shortness of breath were significantly less common in the active group than the control group. Summary: Although initial results look promising, further follow up of the ongoing cohorts is required before any recommendations can be made within the public health context.