Patch testing is a procedure used to diagnose skin allergies that manifest as Allergic Contact Dermatitis. ACD is a rash in the skin that resembles eczema — an itchy, red, scaly rash, which appears several days after the skin comes into contact with something that it is allergic to.
You can become allergic to many types of things that touch the skin on purpose, both frequently and infrequently, such as fragrance, dyes, and preservatives in our personal care products, metal jewelry, or even the rubber in gloves and shoes. It can be quite challenging to identify the responsible allergen, and or the source of the exposure to the allergen, therefore patch testing is useful to elucidate what you are reacting too and what you aren’t reacting to.
Patch testing is generally composed of three visits. On the first visit, we apply panels of small patches, or chambers, to the skin of the back with hypoallergenic tape. These patches are films or little samples of specific chemical isolates that represent possible allergens. At a minimum, we test 36 patches, selected on the basis of being the most common skin allergens. Sometimes we test as many as over 100 patches depending on the patient’s relevant exposures. We can even test patients to their own personal care products directly!