Q: What Is Allergic Contact Dermatitis? A:
What is Allergic Contact Dermatitis? Most people are very familiar with Allergic Contact Dermatitis (ACD) although they may not realize it. The itchy skin rash caused by exposure to poison ivy is a classic example of ACD. Another example of ACD is nickel allergy in someone who reacts to costume jewelry or the metal button on their jeans.
Unfortunately all cases of ACD are not this clear-cut. There are numerous substances, called “allergens,” that can cause dermatitis in sensitized individuals. Many of these allergens are difficult to identify. For example, a patient may be allergic to various preservatives or fragrances in their personal care products. Patients may even be allergic to ingredients in the medications they are using to treat their rash.
In cases such as these, patch testing is used to identify the specific allergens. Patch testing is a safe and painless process. Small amounts of suspected allergens are placed onto tape and then applied to the patient’s back. Unlike “scratch” or “injection” testing, there are no needles involved. The tape is removed after two days and a reading is made to check for reactions (a red spot at the location of a particular allergen.) A final reading is made several days later.
Common allergens include metals, fragrances, topical antibiotics, and preservatives. The top 10 allergens recently identified by the Mayo Clinic Contact Dermatitis Group (MCCDG) were: Nickel, Balsam of Peru, Gold, Neomycin, Fragrance mix, Thimerosal, Cobalt, Formaldehyde, Benzalkonium chloride, and Bacitracin.
Allergic contact dermatitis can be very frustrating for patients when they do not know what is causing their rash. But with patch testing, the offending allergens can be identified and successfully avoided.