We are exposed to a large amount of potentially antigenic substances when we take aliments. Normally the mechanic, enzymatic and immunitary functions avoid the development of deleterious phenomena. Thus, when these mechanisms fail intolerance, idiosyncrasy or allergic reaction could be presented to the diet components. The adverse reactions to the aliments are present in one to three percent of the general population, while this occurs in the eight percent of the children under three years old. The clinical manifestations may comprise from abdominal pain pictures to anaphylactic shock. The symptomatology depends on age of the patient and the amount and kind of ingested food. The diagnosis must be establish on bases of careful anamnesis and physical examination. To confirm the diagnosis cutaneous test for immediate hypersensibility and the determination of specific IgE antibodies (RAST, ELISA) are used. The basic treatment consists in the withdrawal of the causative aliment and not on non-proper diets for the patient.