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About Photo 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, an allergy to UV light, or a chemical that is activated by sunlight. This is not the same test done by your immunologist or allergist. Photo patch testing is done by placing small amounts of chemicals on your back and exposing them to UV light. We will also test your skin by shining small amounts of UV light on your skin.

What to Expect During the Week of Photo Patch Testing

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


  • Arrive 15 minutes prior to your scheduled appointment. Patch testing evaluations are involved and can be lengthy.
  • Expect to be in the office for two hours.
  • The doctor will evaluate your skin and the nurses will place the patches on your back and possibly the upper arms.


  • The nurses in phototherapy will perform a light test by exposing the skin on your left forearm and/or lower back to different strengths of UVA and UVB light. Wear or bring a long-sleeved shirt, ankle-length pants and closed-toed shoes for the appointments with Phototherapy.


  • The patches are removed from your back and the initial interpretation is recorded 48 hours into the test. Afterward, the nurses in phototherapy will read the results of the light test and expose some allergens to UV light. Wear older or dark colored clothing to your appointments. The testing can stain clothing. We will be using a highlighter and skin marker on your back that may transfer to your clothing.


  • The doctor reads the final results of the test (96 hours into the test) and reviews them with you at this visit. If you develop a late reaction at the test sites after the appointment, take a picture of the area and call the office during normal business hours at 215-662-2737, as soon as possible.
  • Depending on the extent of your patch testing, your visit on Friday could be lengthy, so please allow adequate time.


There is a $200 no-show fee if your appointment is not canceled by 3pm the Wednesday prior to your appointment. You will not be rescheduled for a new test date until that payment is received and credited to your account.

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