Elizabeth Otero, M.D.


What is a Patch Test?

A patch test is a skin test used to help determine the cause and nature of your contact dermatitis. A patch test helps to identify any substance(s) causing your dermatitis so that you may avoid exposure to the source of your skin rash.

When should patch testing be done?

Patch tests are done to help determine if your skin rash is contact dermatitis and not another condition such as psoriasis or eczema.

How is patch testing done?

A number of different allergens that may be causing your rash are applied in very small amounts on a small area of skin on your upper back, which is covered so it's watertight. The patch test is usually left on your back for two days. When you return to the office the patches are removed and the test is read at 48 hours, you will then return two days later for a second reading at 96 hours.

What to avoid prior to patch testing?

Avoid oral steroids for two weeks prior to testing. Avoid steroid injections for
one month prior to testing.
Avoid all antihistamines for five days prior to testing. These include: prescription
and over-the-counter medications used for colds, allergies, and reflux symptoms.
Ex: Benadryl, Atarax or Hydroxyzine, Claritin, Alavert, Clarinex, Allegra, Zyrtec,
Zantac, Tagamet or Cimetidine or any antihistamine containing medications.
Avoid topical corticosteroid on the back area ex: Hydrocortisone cream, Elocon,
Diprolene etc.. .for two weeks prior to testing.
Avoid topical immunosuppressive on back area ex: Protopic or Elidel for two
weeks prior to testing.
Avoid systemic (oral, injected) steroids for two weeks prior to the patch test.
Avoid sun exposure and sunburn on back area for one week prior to testing.
Avoid lotions, creams on back area for 24 hrs prior to testing.
Avoid shaving back area prior to testing.
After the patches are on your back, you should strictly avoid swimming, bathing,
showering, and any physical activity that causes sweating, (sponge bath is OK
but not over the patch test ) until after the second reading.