Factors determining development of allergy in infants

For an infant to develop allergy (atopy), three main factors seem to be needed: genetic predisposition, allergen exposure, and contributory factors. The role of genetics seems to be mainly in transmitting a general atopic constitution and controlling the general IgE response. Together with environmental exposure, genetics possibly plays a role in determining the allergic shock organ and the specific offending allergen. Of the vast number of environmental allergens, food by far seems to be the major one in infancy, followed by indoor allergens then outdoor aeroallergens. Several intrinsic and extrinsic contributory factors can enhance the development of allergy, perpetuate its chronicity, or facilitate precipitation of symptoms. These factors can be immunologic defects, gastrointestinal diseases, infections, or nonspecific irritants such as tobacco smoke inhalation. Understanding all these factors is essential in formulating any program for allergy prevention in infants.