‘Patch test’ is the only way to find out how your skin will react to certain products even if you had no allergic reaction with it in the past. It adds an extra layer of security to your skin treatment and it’s essential to have one. The most common sensitizers are hair dyes, sunscreens and topical non-steroidal anti-inflammatory drugs.
When do you need a patch test?
- If you suspect or have contact allergy
- Before skin treatment
- Before trying new hair dye
- Before trying new skin product
How you can do a patch test?
- Wear the patches either on your back or arms; take a few patches.
- During the patch test, make sure the patches must not get wet at all.
- The patches may expose to a number of substances that can cause contact dermatitis.
- It does not involve any needles and only potential allergens are applied on the patches.
- After 48 hrs you can remove the patches and the irritated skin at any patch site may indicates allergy.
What is Photo-patch tests?
An advanced patch tests done by dermatologist in the clinic when they suspect contact allergy in the skin to certain substance. This test is done with UV light after the patches are removed by exposing the skin to a small dose of long wave ultraviolet light (UVA). The dose of UVA used is way smaller than UVA required to cause sunburn.
Minimal erythemal dose (MED) testing: a small area of the back skin is exposed to a series of incremental doses of UV radiation. Some groups describe performing MED’s for UVB alone, UVA alone, both UVA and UVB.