An additive is a substance added to foods for preservation, coloration and some other purposes. Additives are numerous and include benzoates, metabisulphites and azodyes. The prevalence of adverse reaction to additives is 0.03-0.5%. Adverse reactions to additives occur in 20-25% of patients with aspirin intolerance and in 10-20% with chronic recurrent urticaria. IgE-mediated hypersensitivity, resulting in acute allergic reaction, has been described for azodyes, ethylene oxide and penicillin, and delayed-type hypersensitivity for nickel salt. A list should be provided of foods containing the additive that the patient does not tolerate. Clear labelling of packaged food helps to avoid accidental exposure.
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