Patch Testing for Allergic Contact Dermatitis

Penn Dermatology uses a targeted patch testing technique to thoroughly identify external substances causing allergic contact dermatitis.

Unlike pre-packaged skin patch tests, Penn's customized and unique testing method to treat allergic contact dermatitis provides a significantly higher chance of identifying the offending allergen and treating these skin problems.

How to Prepare for Patch Testing

Please bring all items that you put on your skin, nails and hair to your first patch testing (see below). Keep in mind we do not patch test to your soaps, cleansers, shampoos, toothpaste, mouthwash, household cleaners or laundry detergent. But we are still interested in the ingredients. Please take photographs of the brand of the products and ingredient labels and have these available at the time of your visit. Please also bring all previous medical records related to your skin rash including biopsy results and blood test results.

  • Moisturizing creams or lotions
  • Perfume or cologne
  • Aftershaves
  • Shaving cream
  • Foundation
  • Blush
  • Eyeshadow
  • Mascara
  • Make-up remover
  • Lipstick
  • Lip balms
  • Hair sprays, gel, mousses, conditioners
  • Nail polish and hardeners
  • All natural or organic creams
  • Essential oils
  • Homeopathic or ayurvedic creams
  • Over-the-counter cortisone and anti-itch cream
  • Antifungal creams
  • Antibiotic ointments such as Neosporin, Bacitracin, triple antibiotic cream
  • Wet wipes
  • Sunscreens
  • Insect repellent
  • Anti-aging creams
  • Over-the-counter and prescription eye drops
  • Unused sanitary pads
  • Prescription creams and ointments applied to skin
  • Gloves used at work or home with the brand name and manufacturer

If you suspect your skin rash is caused by your work place, bring in photographs of your work environment and the safety data sheets (SDS) of products that you use in your daily work such as inks, oils, cleansers, glues and adhesives. 

We may need to reschedule your appointment if the following occur:

  • If you receive any kind of steroid injections within one month of your scheduled appointment.
  • If you take oral prednisone within two weeks of your scheduled appointment unless directed by one of our patch test dermatologists.
  • If you apply prescription cortisone-containing topical creams or ointments to your back within one week of your scheduled appointment.
  • If your back is exposed to ultraviolet (UV) light from the sun or tanning booths at least two weeks prior to your scheduled appointment.
  • If your back has a rash at the time of patch testing.

The purpose of patch testing is to determine if your skin rash is caused by an allergy to certain chemicals that come in contact with your skin. The test is done with chemicals placed on tape then placed on your back. This is not the same test done by your immunologist or allergist.

It is a weeklong procedure. Office visits are on Monday, Wednesday, and Friday of the same week. There are no appointments on Tuesdays and Thursdays. 

You may shower and apply deodorant the morning of your first appointment. You may NOT shower or bathe again until after your last appointment on Friday.


The doctor will evaluate your skin, and the nurses will place the patches on your back, possibly the upper arms. On average we test to over 100 substances.


The patches are removed from your back, and the initial interpretation is recorded, 48 hours into the test.


The doctor reads the final results of the test, 96 hours into the test, and reviews the results with you at this visit.

A positive patch test will be red, raised, and itchy possibly lasting several weeks. Sometimes the skin will blister resulting in discoloration over the area on your back that may take time to fade.

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