Contact Dermatitis

What is contact dermatitis?

Dermatitis is one of the most common skin conditions in the United States.  Fortunately, the main cause of dermatitis, contact with environmental factors, is easily curable.  This can only be done once the triggering chemical is discovered through a process called patch testing.

Contact dermatitis most commonly involves the skin of the hands and face but can occur on other areas such as the waist, legs and chest.  One example of this is the reaction many people have to nickel.  The itchy, red, bumpy rash that occurs with “cheap jewelry” is often due to contact dermatitis triggered by this metal.  This same reaction can also occur with exposure to certain chemicals in nail polish, hair dye, contact lens solutions, and sunscreens.

Contact dermatitis is one of the few skin conditions that is completely curable.  If the specific allergen is identified and avoided, the rash will resolve without further need for steroids and other medications.  This has the added benefit of improving the quality of life of those suffering from this form of dermatitis.

How is contact dermatitis diagnosed?

Contact dermatitis can only be diagnosed through patch testing.  This is different from standard allergy testing for environmental and food allergies which involves scratching the skin.  Patch testing relies on a slower moving part of the immune system called T cells.  This means that the tests cannot be done in the 15-20 minutes that scratch tests typically take but rather involves three visits over one week’s time.  A day-by-day review of patch testing is on the back of this pamphlet.

Most allergists and dermatologists are able to offer ‘limited’ patch testing.  This typically involves 24 common allergens in a pre-made patch.  While this is an appropriate screen for contact dermatitis, only about 1 in 3 patients with contact dermatitis will have their causative chemical found in this way.

We are proud to offer a more extensive series of patch tests.  Our patch testing includes 50 chemicals which improves the likelihood of finding the correct chemical causing the dermatitis.  Also, the patch material we use is made within 2 weeks of your appointment to ensure that the chemicals are ‘fresh’ and give your immune system the best chance of displaying a reaction to them.

Patch testing – day by day

  • First visit (Monday): You will come to the clinic and have the patch tests applied to your back and taped to secure them.  This visit will last approximately 15 minutes.
  • Second visit (Wednesday): You will come back to the clinic and the patches will be removed.  After 5-10 minutes, the physician will come in to review the skin for any positive results.  The back will be marked with a pen to show where each patch was placed.  Please wear dark colored clothing for this visit as there is a chance that the pen marks may bleed onto clothing.
  • Third visit (Thursday/Friday): You will return once more to the office and change into a gown.  The physician will review your back and explain any positive results.  He/she will then access a database to provide you with products that do not contain any of these chemicals and are therefore safe to use.  This visit may last 30-60 minutes.


Patch testing involves applying individual chemicals (loaded onto trays) to the back.

Important considerations for patch testing

The chemicals are very sensitive to water so it is important that you not get the back wet for the duration of the patch test session.  This typically runs from the first visit on Monday to the last one on Friday.

With patch testing, you may experience itching on the back if you are allergic to any of the chemicals.  You may also experience a worsening of your rash during this week as your immune system is being tested.  If you experience any pain or burning, please contact the physician who placed the patches.

The CARD Database

The Contact Allergen Replacement Database is an incredible resource that we will use on the date of your final patch visit.  The database will provide you with a comprehensive list of products (for hair, skin, nails, etc) that do not contain any chemicals that you are allergic to.  This will allow you to avoid these chemicals and provide rapid relief of your dermatitis.

This is a handout from the Asthma and Allergy Affiliates reviewing current understanding of contact dermatitis and diagnosis via patch testing.  These handouts are intended for our patients and are not a substitute for discussing your (or your child’s) unique situation with one of our physicians.