Patch testing

Patch testing finds out which substances cause an allergic rash on your skin, known as allergic contact dermatitis. Common culprits include fragrance, preservatives, metals like nickel, hair dye, rubber and ingredients in skin care and cosmetics.

It is different from the skin prick tests allergists use for food or seasonal allergies.

Who it may help

• Rashes that keep coming back without a clear cause
• Rashes on the hands, face or eyelids
• Eczema that is getting worse or not responding to treatment
• Rashes that may be related to work

What to expect

Visit 1: small patches with test substances are placed on your back. Visit 2 (about 2 days later): the patches are removed and your skin is checked. Visit 3 (a few days after that): a later reading, since some reactions take time to show up. Additional readings may be needed.

Keep your back dry during testing, so no showers or heavy exercise that makes you sweat. Ask your provider which medicines or skin products need adjustment. Do not stop prescribed medicines on your own.

Results

If you react to something, we give you a list of what to avoid and where it is found, and help you choose safer products.

Where it is offered

Patch testing Q&A

Related care

• Contact dermatitis and skin allergies
• Eczema and dermatitis
• Rashes