Some patients who suffer from asthma, rhinitis or urticaria undergo exacerbation of symptoms following ingestion of foods or beverages containing azo dyes, sulphur dioxide or benzoates, which are used as preservatives. These patients may be mistakenly thought to be suffering from specific food allergies. A dietary is presented which is free from these additives. Drugs and their coatings and capsules may also contain azo dyes and these should be avoided by patients on an additive-free diet. Four cases are reported illustrating recovery, one from asthma and three from chronic urticaria after commencing this diet.