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QUESTION: Is allergen exposure the major primary cause of asthma?
Data source
Medline search (from 1980).
Study selection
English language studies were selected if they were longitudinal or cross sectional studies of the relation between allergens and asthma. The review focused on primary causation studies that reported the amount of allergen exposure. Studies that used bronchial hyperresponsiveness in the definition of asthma were excluded. Studies of selected populations were used when no information from population based studies was available.
Data extraction
Data were extracted on age, allergen levels, asthma prevalence, definition of asthma, and population attributable risk.
Main results
Results are reported for longitudinal studies only. No population based studies were found on the relation between allergen exposure during infancy and asthma risk after the age of 6 years. In 1 randomised controlled trial, 160 infants with a family history of atopy were allocated to prophylaxis (avoidance of house dust mite allergen and allergenic food) or no …
Footnotes
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Sources of funding: Health Research Council of New Zealand and Guardian Trust (Trustee of the David and Cassie Anderson Medical Charitable Trust).
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For correspondence: Professor N Pearce, Centre for Public Health Research, Massey University Wellington Campus, Private Box 756, Wellington, New Zealand. Fax +64 4 3800 600.