Skip to content

Contact Dermatitis (Patch Testing)

Massachusetts Dermatology Associates offers its patients on the North Shore, MA one of the largest available panels of allergens to test for contact dermatitis.

Frequently Asked Questions (Contact Dermatitis-Patch Testing):

What is contact dermatitis?

Contact dermatitis is inflammation of the skin provoked by contact with certain substances. This inflammation can be either irritant or allergic.   Everyone who comes into contact with certain caustic substances (e.g. alkali, acids) will develop some degree of irritant contact dermatitis.   On the other hand, there are certain substances (e.g. dyes, preservatives, fragrances) to which a minority of the population are truly allergic.   Even small amounts of allergens can provoke allergic contact dermatitis (redness and itching) in sensitized individuals.   Patients often wonder if they should see an allergist or a dermatologist for their skin rash.  Allergic contact dermatitis, which is typically a delayed response (taking days to develop after an exposure) is typically evaluated by a dermatologist; whereas, allergy to inhaled or ingested agents such as pollens, ragweed, and foods are typically an immediate response (taking minutes to develop after an exposure) is usually managed by an allergist.

What is patch testing?

Patch testing involves the exposure of your skin to arrays (patches) of allergens to test for the presence or absence of an allergic response (i.e. testing for allergic contact dermatitis). In most cases we test for 80 of the most common contact allergens.   If you have a contact allergy, this test has an approximately 70% chance of uncovering it.  After determining if an allergen is relevant to your rash, you can then avoid that substance, often leading to improvement of your skin condition. Please note that patch testing does not always explain the cause of a skin reaction or rash, and does not include environmental or food allergy testing.

Are there any risks associated with patch testing?

Discomfort (burning/itching) at patch sites, flare of dermatitis, hyper/hypopigmentation, scarring as a result of strong allergic reactions (rare), inadvertent sensitization to patch materials (rare), and anaphylaxis (very rare). Pregnant or lactating women should NOT undergo patch testing.

Are there alternatives to patch testing?

Instead of patch testing you could try to eliminate suspected products from your environment. After successful elimination it can take several weeks (often over a month) until improvement of your rash

Does my insurance cover patch testing?

Most insurance plans cover patch testing. To be certain that your particular plan covers the treatment, we recommend that you call your insurance company and verify coverage of the following codes  (Diagnosis code = L23.9; Procedure code = 95044, quantity 80 patches)

Are there any medicines or activities to avoid before and during patch testing?

  • Please let us know if you have recently been prescribed prednisone (oral steroids) or a steroid injection, as they can affect patch test results. Antihistamines (i.e. Benadryl, Zyrtec, etc) will not interfere with patch testing.
  • If you are using topical medications, do not apply them to the back for 5 days prior to your appointment
  • If you use over-the-counter moisturizers, do not apply them to your back for 2 days prior to your appointment
  • Avoid sun exposure to your back for 2 weeks prior to patch testing
  • After patches are placed it is critical to keep area dry:
    • YOU ARE NOT PERMITTED TO SHOWER DURING THE WEEK. Washing hair in a sink and sponge bathing is OK as long as patches remain dry.
    • Avoid strenuous activity or exercise that could make you sweat, as well as movements that could cause the patches to come off; reinforce loose patches with tape (paper tape preferred)

What is the schedule for the three patch test visits?

  • 1st visit (Monday): Patch tests are applied
    • It is helpful to wear loose-fitting clothes. You will meet with the testing provider and your questionnaire will be reviewed.  Tiny quantities of materials in individual square plastic chambers will be applied to the back. They will be kept in place with special hypoallergenic adhesive. The patches are to stay in place and remain undisturbed for 48 hours.   Itching is a good sign, indicating potential positive reactions!
    • If you develop extreme itch/pain call the office for further instructions. If it is after hours, try Benadryl and please call at 8 AM the next day.   If it can’t wait until morning, call the main number (978-225-3376) and you can be connected directly with Dr. Cummins.
  • 2nd visit (Wednesday): Patches are removed for 48 hour reading
    • Remember that you may not wash your back until after your final (3rd) visit. Should you become allergic to one or more of the substances, an itchy rash or redness will appear at the corresponding test area.  Please wear an old or dark colored shirt to this visit since the sites will be marked with a blue marker (which could stain clothes).
  • 3rd visit (Friday): Final reading at 96 hours
    • Please bring in your commonly used products from home to your 3rd visit. If the products do not have ingredient labels and you have internet access, please take the time to find a list of ingredients.  This is important in helping to determine the cause of potential reactions.
    • The marked areas on the back must still be visible at this appointment. The provider will examine your back and look for any positive findings.  Further instructions will be given based on findings.

If I want to find out more about patch testing and contact allergens, what are the most informative online resource?

  • Useful informational websites:
    • has videos about your relevant allergens
    • is a database listing products that are safe for you to use
    • is the website for Vanicream (hypoallergenic products)


– We see many patients with eczema which is an itchy rash with redness and scaling. And most of these people have what is called atopic dermatitis. Which is a type of eczema that people inherit from their parents. There’s generally no identifiable environmental trigger.

– Telling atopic dermatitis patients that just like high blood pressure this is a chronic condition. There’s no cure but we can manage it successfully with moisturizers, good skin care, and topical steroids. An important subset of patients with eczema, don’t have atopic dermatitis. They have an allergic contact allergy to a substance in their environment. Allergic contact dermatitis, as it’s called, is the result of an allergen coming in direct contact with the skin. It’s not the same as allergies to pollen, dust mites, or foods, which are systemic allergies caused by breathing in or ingesting allergens.

– Fortunately, we are able to perform a specialized test to figure out which contact allergen is causing a particular patient’s dermatitis. We call this test, patch testing. With patch testing, we attach several patches containing the most common contact allergens to a patients back. Those patches need to stay in place for 48 hours in order to recreate the allergic reaction. The way it works is this, we see patients undergoing patch testing on Monday. At which time we attach 80 of the most common allergens to their backs using adhesive patches that have small wells containing samples of the allergen in question. The patches are placed in precisely the correct orientation so that we know the exact location of each allergen.

– The patient goes home with the patches affixed to their back. And they’re given careful instructions to keep the patches dry and to avoid exercise if possible. Because stretching and sweating could dislodge the patches. On Wednesday the patient comes back to the office and that visit the patches are removed and an initial reading is done. Even with the patches off the patients are still instructed to keep their back dry from Wednesday to Friday. On Friday, patients come back to the office and the final reading is completed. At that visit the patients are also educated on what they’re allergic to and what they can do to avoid contact with the offending chemicals in the future.

– And additionally as a member of the American Contact Dermatitis Society we have access to a database which allows us to give patients an electronic list of all products that are actually safe for them to use for that worry.

– This is a test that can for some patients really be life changing. It can get many of them back to work. And it removes a significant stressor so that they can focus their energies back on things that they really enjoy. Finding the cause of patients long standing dermatitis is really one of the most satisfying parts of our work.

Back To Top
Skip to content