What is patch testing for foods? Can patch testing help determine which foods are causing my sons EE?
Patch testing or atopy patch testing is another way to test for food allergies. To better understand patch testing, the differences between regular allergy testing and patch testing should be explored. The standard or regular tests for food allergy are scratch test or prick skin test and RAST blood testing (also called CAP-RAST testing). Prick skin testing examines IgE-mediated reactions. IgE-mediated reactions occur within seconds to hours after ingestion of the food causing hives or anaphylaxis. Patch testing examines for non-IgE mediated reactions. These reactions are often delayed, occurring hours to days after ingestion of the food. Many patients with non-IgE mediated reactions have difficulty in identifying the food causing the reactions. Patch testing was first done in 1890s for reactions to perfumes, dyes and metals. Patch testing for foods have been done since 1990’s in Europe and in the US since 2000. Another major difference between prick skin tests and patch testing is the
