Mohs Surgery & Dermatology Center
A patch test is common test used to determine what is triggering an allergic reaction by the skin. This allergic reaction is referred to as allergic contact dermatitis.
The trigger of the allergic reaction is called the allergen. Common allergens include metals ( nickel), fragrances, adhesives, fragrances and other chemicals.
During the test, different potential allergens are applied to the skin in the medical office and then left in place to give time for the skin to react. Your doctor will select allergens that are suspected to be possible triggers of the rash.
A small amount of each selected substance is placed on the skin, usually on your back, and left in place for 2 days.
You will be remove the substance from the skin after the test period has been completed. You will usually be instructed to do this yourself at home.
After 3 days, you will return to the office and your doctor will look at your skin to determine which substances have triggered a reaction, if any.
If it often necessary to return to the office again after 4-5 days for another check to be sure that no delayed reactions have occurred.
Positive reactions can last for several weeks and can itch or be irritating. Your doctor may give you a medication to control the itch.