An allergen is a substance (antigen) that causes a hypersensitivity reaction through the IgE (immunoglobulin E) response. IgE response is normally used against parasite defense but some individuals respond to environmental antigens.
Although over 160 foods can cause allergic reactions, however just eight foods (called the Big-8) that cause 90 percent of these reactions:
Milk (cow), egg, soybeans, fish, tree nuts, peanuts, shellfish, and wheat.
Breakdown of Food Allergies by Type
Commun Food Allergens