Indications for patch tests in patients with suspected drug hypersensitivity

Dr Barbara M. Mathes is a clinical associate in dermatology at the University of Pennsylvania and immediate past president of the Women’s Dermatologic Society.

What are the indications for patch tests in patients with suspected drug hypersensitivity?

Barbara M. Mathes, MD: Can patch tests be helpful in identifying drugs that one may have a hypersensitivity reaction to? The answer to that is, “Sometimes and only with certain types of rashes.” There are few drugs that there is about a 50% chance that the test will predict whether or not you will have a reaction if you have already had a reaction to that drug.

Drugs that are most common to be responsive to the patch testing are the carbamazepine family—used for seizure disorders, epilepsy—and a drug called abacavir, which is an antiviral drug that we often use in people with a retrovirus or human immunodeficiency virus (HIV). For other allergic reactions, there is often less than a 25% chance that the patch testing will tell us if you are truly allergic to the drug.