Food allergy represents a highly up-to-date and continually increasing problem of modern man. Although being present in all ages, it most often occures in children aged up to three years. Sensitization most often occurs by a direct way, but it is also possible to be caused by mother?s milk, and even transplacentally. Predisposition of inadequate immune response to antigen stimulation, reaginic or nonreaginic, is of nonselective character so that food allergy is often multiple and to a high rate associated with inhalation and/ or contact hypersensitivity. Also, due to antigen closeness of some kinds of food, cross-reactive allergic reaction is also frequent, as is the case with peanuts, legumes and tree nuts or cow?s, sheep?s and goat?s milk. Most frequent nutritive allergens responsible for over 90% of adverse reactions of this type are proteins of cow?s milk, eggs, peanuts, tree nuts, wheat, soy, fish, shellfish, crustaceans, and cephalopods. Allergy intolerance of food antigens is characterized by a very wide spectrum of clinical manifestations. Highly severe systemic reactions, sometimes fatal, are also possible. The diagnosis of food allergy is based on a detailed personal and family medical history, complete clinical examination, and corresponding laboratory and other examinations adapted to the type of hypersensitivity and the character of patient?s complaints, and therapy on the elimination diet. A positive effect of elimination diet also significantly contributes to the diagnosis. Although most children ?outgrow? their allergies, allergy to peanuts, tree nuts, fish, shellfish, crustaceans, and cephalopods are generally life-long allergies.