Urticaria and food allergy

Urticaria (or angio-oedema) and food allergy

• patients or their parents frequently analyse foods, food additives/preservatives/dyes eaten over the previous 24 h or longer in the search for a connection with symptoms
  • there is no rational basis for this because in genuine food allergy, symptoms usually occur reproducibly within 60min of exposure to the offending food
  • occasionally, exceptions occur for example in some patients wheat allergy is clinically manifested only in association with exercise

Unless there is a relationship to a particular food trigger, either by ingestion, or contact (localized contact urticaria), IgE-mediated food allergy can usually be excluded as a cause of urticaria/angio-oedema particularly if the symptoms come on overnight or are present first thing in the morning

• allergic food reactions do not produce an urticarial rash (with or without angiooedema) lasting several days, nor rashes/swellings commencing several hours after ingestion of food
• urticaria due to IgE-mediated food allergic reactions seldom occur in isolation i.e. additional symptoms are usually present such as oropharyngeal itching and discomfort, wheezing, vomiting or abdominal pain

Reference:

• (1) Powell RJ et al; British Society for Allergy and Clinical Immunology (BSACI). BSACI guidelines for the management of chronic urticaria and angio-oedema.Clin Exp Allergy. 2007 May;37(5):631-50.