What is patch testing?
Patch testing allows your dermatologist to diagnosis allergic contact dermatitis. It is a simple procedure that assists in identifying causative agent(s). During the test, a patch test will create a series of small patches which will include a small amount of different allergens that are known to cause reactions. The patches are applied to the arm or back, depending upon the recommendations of the dermatologist. There is no pain associated with patch testing because unlike scratch tests, there are no needles used when the patches are being applied. The patches are left on for a period of time (roughly two days) and then examined by the dermatologist. Sometimes, the doctor will have you return again after the test to see if there is a delayed reaction to the allergen.
With this very helpful test, your dermatologist can you help you avoid products that cause allergic reaction.
What is photo-patch testings?
Some allergens react when exposed to light. Photo-patch testing is a special kind of patch test that allows an allergen be exposed to light so the doctor can compare between those exposed to light and those not exposed to light.