Patch Testing

Patch testing is a process used to try to find out what things are causing allergic reactions in your skin, such as contact dermatitis. Based on the kind of rash you have, your doctor will decide which substances to use for testing.

Test chambers with a small amount of each substance are put directly on your skin, usually on your back. These are left in place for 48 hours. At the end of that time, you will be asked to remove the test chambers at home. After 72 hours you will return to the clinic and the doctor will look at your back to see if any reactions have occurred.

Usually it's necessary to come back after 4-5 days for another skin check to make sure no delayed reactions have taken place. Positive reactions may persist for several weeks. Your doctor may give you medicated creams to alleviate any symptoms (like itching) associated with a positive reaction. Colored spots may also persist at the test sites following patch testing. This is normal.

Watch a video on patch testing.