Figure 1From: Childhood infections and asthma: at the crossroads of the hygiene and Barker hypothesesOverview of the development of childhood asthma. Fetal environmental and genetic influences lead to a specific immunophenotype in the newborn. Subsequent interactions with external environmental exposures (including infections), in conjunction with genetic predisposition, lead to the development of asthma. It is probable that all three components (developmental, genetic, and environmental) are necessary for asthma to occur.Back to article page