Diagnosis of food allergy

Food allergy can rarely be diagnosed by laboratory methods alone. The best approach is one which combines clinical observations with attempts to confirm the diagnosis by laboratory tests. In principle, the patient is put on a complete exclusion diet to see if the symptoms are thereby ameliorated. Attempts are made to provoke these by restoring items of diet in a planned sequence. It is usually necessary to intersperse these dietary items with placebo substances, that is, dummy foods so that both the doctor and the patient are free from bias in interpreting the results. The demonstration that disodium cromoglycate prevents this provocation provides additional evidence that a particular food is responsible for the disease symptoms. In addition, beneficial results with this drug indicate that the reaction is indeed allergic in nature.