Is there any role for allergen avoidance in the primary prevention of childhood asthma?

In this article we discuss 3 hypotheses to attempt to understand why preventive measures thus far studied with the aim of preventing (or delaying) the development of asthma have shown such disappointing results. The most likely explanation is that the development of a multifactorial disease, such as asthma, is extremely difficult, if not impossible, to prevent by eliminating only one risk factor. In a meta-analysis we investigated the effect of a multifaceted and monofaceted intervention in 10 prospective birth cohorts of a total of 3473 children on a diagnosis of asthma. Multifaceted intervention studies had an odds ratio (OR) of 0.73 (95% CI, 0.55-0.97), whereas the monointervention studies had an OR of 1.22 (95% CI, 0.83-1.78) in patients younger than 5 years and an OR of 0.52 (95% CI, 0.32-0.84) versus 0.93 (95% CI, 0.66-1.31) in patients older than 5 years. We therefore hypothesize that studies with a multifaceted approach will have a much greater chance of being successful than studies using a monofaceted approach, with the latter being unlikely to yield a clinically relevant reduction of asthma.