The environment and risk factors for atopy.

Atopy is the genetic potential to manifest the trinity of classic allergic diseases--atopic dermatitis, allergic rhinitis, and asthma. All have been observed to have increased over the past several decades. The interplay of the genetics of atopy with various environmental exposures may manifest itself in the form of allergic phenotypes or paradoxically may actually suppress the allergic response. The hygiene hypothesis offers an explanation of why certain environmental exposures early in life may suppress or activate clinical disease. Primary prevention is directed at preventing the clinical manifestations of atopy by suppressing or delaying the onset of allergic sensitivity. Studies of primary prevention have brought mixed results. Secondary prevention is directed at reducing or removing triggers in the environment of the sensitized individual. Secondary prevention measures directed at one allergen have not proven successful. Comprehensive intervention programs dealing with both allergens and other potential triggers appear beneficial.