Contact Dermatitis
What are patch tests?
A patch test is the application to the skin of a small amount of the material suspected of causing the rash. The "patch" is usually placed on the healthy skin of the forearms or back, covered with a small bandage or band-aid and usually left on the skin for 48 hours. (If you feel intense itching or burning from the patch, it should be removed immediately.)
A positive patch test shows redness, swelling or even blistering of the small area where the substance was in contact with the skin. It is actually a miniature reproduction of the rash, and thus pinpoints the trouble-making substance.
After careful consideration of your medical history and study of the location and appearance of your rash, your doctor will decide whether you need a patch test, and what substance should be tested. Never try a patch test yourself; it may cause serious trouble.
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