Please welcome our newest dermatologists, Dr. Cory Pettit and Dr. Dan Flood, who joined COSC this year!


How Patch Testing Works

Patch testing helps to diagnose allergies caused by physical contact to allergens such as fragrances, metals, and dyes. This test is different from allergy prick testing performed in an allergist’s office, which diagnoses allergens that are inhaled or ingested such as pollen, nuts, and pet dander. Importantly, there are no blood tests for contact allergens.

How Patch Testing is Performed

Patch testing is composed of three appointments. At your first appointment, small amounts of concentrated allergens are placed on strips of tape which are applied to your back and left in place for two days. At your second appointment, the tape strips are removed, and the physician performs an initial read to see if you reacted to any of the allergens. Your third appointment is the following day, where the physician performs a final read, as many allergens take up to 72 hours from the time of application to react. If any of the tests are positive, you will be provided with a handout with information about the allergen, as well as access to a website and app that can generate lists of safe product lists. For allergen selection, we use the North American Comprehensive Patch Testing Series, which tests for the 80 most common contact allergens. For a full list of these allergens, please visit:

How to Schedule Your Test

Your physician will send a referral to our patch testing team. Once we receive the referral, a member of our team will call you to schedule. The testing is always performed in a series of three appointments that take place on Monday, Wednesday, and Thursday of the same week. Appointments typically last 20-30 minutes.

Before Your Appointment

  • Please bring any personal care products, soaps, topical medications, or other possible allergens to your Monday appointment. We must have these products before your final appointment as the doctor reviews your ingredient lists prior to your final appointment.
  • Do not use oral steroids in the two weeks prior to your appointment. If you are being treated with long-term oral steroids, please contact your prescribing physician and our office to discuss before scheduling.
  • Your back must be clear of active rash on the day of your appointment, as this will make it difficult to see positive results.
  • Do not use topical steroids, tacrolimus, or ruxolitinib on your back for one week prior to your appointment. If these are prescribed for other areas of the body, you may continue to use them.
  • Antihistimines and other allergy medications may be continued.
  • We recommend wearing old or dark clothes during the testing week, as a marker will be applied to your back to mark the sites, and this may stain clothing.

After Your Appointment

  • Do not remove, scratch, or rub the panels, even if they are itching.
  • Do not allow the panels to get wet, as this may lead to them peeling off, or the allergens mixing together. If you need to wash your hair, do not let your back get wet.
  • Avoid strenuous exercise or sun exposure to your back until after testing is completed.
  • Since some of the allergens contain dye or pigment, you may notice black discoloration over the patches. This is normal and not indicative of bleeding or infection.
  • After the panels are removed on your Wednesday appointment, please continue to keep the area dry as the markings must remain intact for your final reading appointment on Thursday.

Patch Testing Cost

Patch testing is covered by the majority of government and private insurance providers. However, as with any medical procedure or test, you will be responsible for any deductible and copay. If you would like to ensure that the testing is covered by your insurance and get a more direct estimate, please reach out to your insurance carrier. Let them know you are being patch tested for contact dermatitis, and provide billing code 95044, 80 units. There will also be two billable office visits, which will be code 99213 or 99214. The diagnosis code is L23.9.