Causes
Atopic reactions are caused by localized hypersensitivity reaction to an allergen. Atopy appears to show a strong hereditary component. One study concludes that the risk of developing atopic dermatitis (3%) or atopy in general (7%) "increases by a factor of two with each first-degree family member already suffering from atopy".
Environmental factors are also thought to play a role in the development of atopy, and the 'hygiene hypothesis' is one of the paradigms available to date that may explain the steep rise in the incidence of atopic diseases. This hypothesis proposes that excess 'cleanliness' in an infant's or child's environment can lead to a decline in the number of infectious stimuli that are necessary for the proper development of the immune system. The decrease in exposure to infectious stimuli may result in an imbalance between the infectious-response elements and the allergic-response elements within the immune system.
Some studies also suggest that the maternal diet during pregnancy may be a causal factor in atopic diseases (including asthma) in offspring, suggesting antioxidants, certain lipids, and a Mediterranean diet may help to prevent atopic diseases.
The multicenter PARSIFAL study in 2006, involving 6630 children age 5 to 13 in 5 European countries, suggested that restrictive use of antibiotics and antipyretics are associated with a reduced risk of allergic disease in children.
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