BACKGROUND: Two factors thought to influence the risk of asthma are the promoting effect of sensitization to house dust mites and the preventive effect of increased omega-3 fatty acids.

Although house dust mite allergen avoidance has been used as a preventive strategy in several trials, the effect of omega-3 fatty acid supplementation in the primary prevention of asthma and allergic disease is not known.

OBJECTIVE: To measure the effects of dietary supplementation with omega-3 fatty acids and house dust mite allergen avoidance in children with a family history of asthma.

METHODS: A total of 616 children at high risk of asthma were enrolled antenatally in a randomized controlled trial, and 526 children remained in the trial at age 3 years. The outcomes were symptoms of allergic disease and allergen sensitization.

RESULTS: There was a significant 10.0% (95% CI, 3.7-16.4) reduction in the prevalence of cough in atopic children in the active diet group ( P=.003; number needed to treat, 10) but a negligible 1.1% (95% CI, -7.1 to 9.5) reduction cough among nonatopic children. There was a 7.2% (95% CI, 10.11-14.3) reduction in sensitization to house dust mite in the active allergen avoidance group ( P=.05; number needed to treat, 14). No significant differences in wheeze were found with either intervention.

CONCLUSION: These results suggest that our interventions, designed to be used in simple public health campaigns, may have a role in preventing the development of allergic sensitization and airways disease in early childhood. This offers the prospect of reducing allergic disease in later life.