How is contact dermatitis diagnosed?

Doctors diagnose contact dermatitis by examining the skin and asking questions. If a person complains of serious itching, a doctor will look for certain signs, including:

• a burn-like rash on the skin
• redness and warmth
• swelling

In severe cases, contact dermatitis can produce skin sores that become scaly and ooze fluid.

To confirm a diagnosis of contact dermatitis, a doctor will ask about your exposure to potential skin irritants, such as poison ivy, nickel and other metals, latex, and others. He or she may then use a patch test to identify the substance that's causing contact dermatitis. To perform this test, the doctor applies a small patch containing a tiny sample of the substance to the skin. If the skin reacts by producing a rash, contact dermatitis is diagnosed. 

Your doctor can diagnose contact dermatitis by looking at your rash and asking you questions. It can be tricky to determine what substance is causing your rash, however. Sometimes there is an obvious cause; for example, if you wear a ring that contains nickel, and you now have a rash around that finger, you are probably reacting to the nickel. If the cause is not clear, your doctor may do a patch test on your skin. First, the doctor may ask questions to discover what substances you have been exposed to. Next, tiny amounts of the suspect substances are placed on small patches. The patches are then placed on your skin. If your skin under a patch reacts, then that substance may be causing your rash.