Patch testing is a type of allergy test performed to determine if someone may have a delayed type of reaction to a chemical or in some cases to a food.
It is most effective at determining if someone may be having a skin reaction caused by a chemical such as a perfume or dye. It usually involves applying a standard series of tests to the skin (using a patch). The patch is left on the skin for 48 hours and any reactions are measured when the patch is removed. It sometimes requires multiple visits to read and interpret the tests. At San Tan Allergy & Asthma we can do patch testing to several different types of materials, such as: chemicals, metals, sunscreens, dental materials, and foods. If there is a test you feel is appropriate that we may not do, you can always suggest it so it can be made available.
In certain instances, such as when eosinophilic GI disease (EGID) is diagnosed, patch testing for foods may be necessary to help determine if a delayed type of allergic reaction may be causing an allergic reaction. The physicians at San Tan Allergy & Asthma offer this type of test as an additional measure to try and determine the cause of the allergic inflammation causing EGID.
A food challenge generally involves giving the patient very small amounts of the food that they are suspected of being allergic to. Gradually they are given increasing amounts of the food and monitored for any type of allergic reaction.
To read more about food challenge testing, see our informational sheet.