Contact dermatitis is an itchy red rash that occurs from a chemical or substance coming into contact with the skin. The most well-known example of contact dermatitis is the rash caused by poison ivy, but contact dermatitis can also occur from everyday exposures such as soaps, cosmetics, jewelry, and hair dye. Some people are exposed to substances at work that may cause contact dermatitis.
To treat contact dermatitis successfully, patients need to identify and avoid the cause of the reaction. The rash typically clears in eight to 12 weeks if the offending substance is avoided.
Diagnosis of contact dermatitis
Diagnosing allergic contact dermatitis is initially based on physical exam and medical history. In cases where patients suffer from a single episode of contact dermatitis or where the cause is apparent, no further testing may be necessary. Chronic and/or intermittent rashes that are not readily explained by history and physical exam often will benefit from further testing. Other tests that may be used to diagnose contact dermatitis and rule out other potential causes of the symptoms include a skin biopsy, culture of the skin lesion, and patch testing.
Who needs to be tested?
If a patient suspects that a skin problem may be caused by an allergy, then patch testing should be done. Many cases of dermatitis or eczema without an obvious cause turn out to be due to an unsuspected allergy. This is particularly frequent with hand eczema. Once an allergen is identified and avoided, the dermatitis can frequently be cured or improved.