What is Contact Dermatitis?

Contact dermatitis is a red, itchy rash caused by a reaction to a chemical substance that came in contact with your skin. It is not contagious. For some people, the reaction is localized, for example earlobe dermatitis from cheap metal jewelry, and for others it is widespread and debilitating.

There’s a wide range of substances that can cause this reaction– from poison ivy and similar plants, to metals, to ingredients in our personal hygiene products. The allergen chemicals are listed in order from highest to lowest frequency in the ‘I am allergic to’ section under patient education tab. It is important to note that the one thing that holds true for all persons with allergic contact dermatitis (ACD) is that to put the rash into remission, there needs to be avoidance of the chemical substance.

For some, the rash can come and go. The underlying mechanism (immunological-science) is complicated, but it basically boils down to the fact that the more your immune system ‘sees’ the chemical, the more it remembers it. If you wear nickel earrings, a nickel-backed watch, and constantly handle nickel keys, you have three exposures to one basic chemical, nickel. Each time your immune system ‘sees’ the chemical, it can recognize the chemical quicker the next time, your immune system remembers it more. Eventually, people can react to very little chemical stimulation because they have a great memory of it, and sometimes the reactions can be all over the body. In strongly sensitized persons, even food can cause them to react! For example very sensitive people with nickel allergy might react to foods high in nickel (such as chocolate, oats, and legumes (like beans and peanuts).

Find a Physician to perform your patch test!

The Art of Diagnosis

Once it has been determined that you are likely to have ACD by history, then you will be instructed on whether or not you will need a patch test. Since its discovery in 1895, the non-invasive ‘epicutaneous patch test’ has been the gold standard test, the best test to confirm that a patient is sensitized to a chemical.

Who needs a patch test?

In order to confirm the diagnosis of ‘ACD’, your provider will take a thorough history and visualize (see) your rash. Sometimes the association with the allergen chemical is obvious. For example a round patch of rash on the wrist which corresponds to the point of where the back of the watch is releasing nickel suggests the role of the watch, and confirmatory testing will not be needed. In a significant number of cases, however, the rash will come and go and it will be difficult to know what is causing it without a patch test. Many rashes can look like ACD and it is important that your seek evaluation by someone properly trained in the evaluation and management of ACD to determine if a patch test is needed.

How is the Patch Test Done?

The test is not invasive, not painful and takes up 5-7 days to complete. Many insurance companies cover this test and you should check with your insurance carrier before you have the test. The chemicals are applied to the skin on stickers for up to 48hours. They are then removed and the sites checked for ‘early reactions’. The patient then returns in 48-96hours after the removal to have the final reading of the patch tests. All positive reactions are then recorded. The patch test expert will then re-review the patient’s history and correlate it with the positive reactions to see if they can help the patient discover the source of the chemical to which they are reacting. One the source of the chemical is identified and avoided, the rash will go into remission (go away).

What Happens After the Patch Test?

Avoidance of allergen chemicals that the person has reacted to on their patch test (been noted to be sensitized to) is the best method of treatment. However, since the chemicals can activate the skin for weeks after exposure, it is important to maintain strict avoidance for at least 6 weeks. In the meantime, cool compresses, topical anti-inflammatory creams (steroids, topical immune modulators), and antihistamines may be needed, while the rash subsides.