Introduction
Contact dermatitis is a common skin condition affecting adults and, to a lesser extent, children. It often occurs with other conditions such as eczema. It is characterized by a rash that is red, itchy, with scale (dried peeling skin). There may also be blisters. It may occur anywhere on the body. There are 2 types of contact dermatitis, allergic contact dermatitis (ACD), resulting from a special type of allergic reaction, and irritant contact dermatitis (ICD), a nonspecific reaction to irritants. Symptoms include a burning stinging sensation with redness, swelling, and peeling. It occurs from an allergic reaction to something coming into contact with the skin on a chronic basis. One should suspect contact dermatitis when the skin condition does not respond adequately to therapy or occurs in a skin distribution not typical for eczema (e.g. a rash around the eyes). A common example would be an earlobe rash or a rash under the pant buckle in an individual with contact dermatitis to nickel. Two common contact allergens are nickel, a substance in metals/jewelry, and neomycin, an antibiotic ointment. There are hundreds of other contact allergens that may be involved.
Diagnosis
The main focus of management is to find the underlying contact allergen. Since the underlying mechanism of this allergy is different from the IgE-mediated allergy commonly seen with asthma, hay fever, and food allergy, patch testing, instead of skin testing, is performed. The contact allergens are placed on the back under devices called Finn chamber. There is a standard panel of common contact allergens called the T.R.U.E. test that may be used. Certain items may be brought from home. The patient generally returns to the office two days (48 hours) and four days (96 hours) later for patch test reading/interpretation. Some patch test reactions, especially topical corticosteroids, and metals may turn positive up to 10 days after application. Click here for an educational handout on patch testing.
Management
The most important aspect of management is avoidance, if the substance causing the reaction can be identified. Your allergist will give you written information regarding what to avoid, and what alternatives are available. In some cases, topical corticosteroids as well as several topical medicines that do not contain steroids (Elidel, Protopic, Eucrisa) may be utilized
