Photo Patch Testing

Instructions


Photo Patch Test is used to detect photoallergic reactions to skin products that may trigger allergies upon sun exposure. If you have rashes over sun-exposed areas such as the face, neck, chest, arms, this test may be appropriate for you.

This test will take 3 clinic visits: Thu-Sat-Mon/Tues. Each visit takes around 30 minutes.

Preparation:

  • Avoid corticosteroids and certain immunosuppressant medications for 2 weeks prior to the testing (check with your doctor before discontinuing any medications).

  • Avoid sun exposure to your back.

  • Do not apply any lotions, creams, or fragrances to the back.

Visit 1 – Thursday:
Two identical sets of patches filled with suspected antigens will be applied to your back. Some itching or discomfort may develop under some chambers.

  • DO NOT ALLOW THE PATCH TEST AREA TO BECOME WET. Avoid showering. Take only shallow baths and wash hair over the sink.

  • Avoid touching the patch test area, as scratching may alter results and cause a false positive.

  • Keep patch test area dry, and wear loose clothing.

  • Avoid topical medications over the patch test area, prolonged sun exposure, and strenuous physical activity that can cause excessive sweating.


If you notice loosening of the test unit, have someone press firmly on the edges, and if needed, apply additional adhesive tape on the edges. If intense burning or itching occurs, call the clinic at (617) 804-6767.

Visit 2 – Saturday:
The first test reading will be done after ~48 hours. One set of patch will be covered with an UV opaque sheet. UV light is going to be shine over the other uncovered set of patch. If an antigen is positive under UV light and negative without UV light, this would suggest a photoallergic mechanism.

Visit 3 – Monday/Tuesday:
The second reading (identical to the first reading) will be done 48-72 hours after patch application. You will receive information about any substance(s) you may be allergic to and be advised on how to avoid these substances. You will also receive information about skin products that do not contain allergens you are photoallergic to for future uses.

Side Effects: Patch tests are safe. You may expect some irritation and redness under the test strip.
If intense burning or itching occurs, call the clinic at (617) 804-6767.

Instructions after patch removal:

  1. Do not wipe off markings over the testing area.

  2. You can take a bath but continue to avoid getting the patch test area wet if possible and do not scrub your back or apply lotion/creams to patch test area.

  3. Come for your 2nd and 3rd visit to see the physician.