Allergy refers to the hyper sensitive reaction by the body’s immune system to any substance (metals, chemicals, dust, pollen, etc.). Dermatologists perform skin tests called Patch Testing to determine the skin’s reaction, identify the allergen (substance that causes allergy) and treat the allergy. These tests are usually performed by application of a tiny amount of allergen onto the skin, either by scratching or pricking the skin or by injecting the allergen.
Patch tests are a method of identifying the allergen that causes contact dermatitis (inflammation, itching or redness of skin which may lead to blisters) and any other skin reactions.
If it’s your first visit, your dermatologist will take a complete medical history, discuss with you about your skin problems, and conduct a thorough skin examination. A patch test is indicated if skin rashes are noticed during the examination. During the procedure, a very tiny amount of nearly 25 allergens are applied as a small patch or disc onto areas of normal skin, usually on the upper back, with the help of a non-allergic tape. These are fixed firmly and allowed to stay in place for 48 hours. In the course of time, you are not permitted to wash the area, expose the area to sunlight, or indulge in activity that might cause sweating. The doctor will remove the patches after 2 days and will examine the area thoroughly to interpret the results. Based on the test results (negative and positive), your doctor will plan the appropriate treatment. Doubtful reactions necessitate additional tests to help confirm the presence of an allergy.
The advantages of patch testing include:
- 2 days of continuous application helps to prove any delayed reactions you might have to any substance.
- You can go to work wearing the patch.
The patch test has no major disadvantages except that the inspection is conducted on a very small area and hence the readings may be biased.