Recurring rash? Patch testing may help identify the cause.

Patch Testing

Skin rashes that keep coming back may be caused by an external allergen rather than eczema or psoriasis. Your dermatologist may recommend an evaluation for a condition called contact dermatitis. Essentially, It is a rash caused by direct contact with a product such as a metal in jewelry, the poison ivy plant, or a preservative in a skin lotion. Treating the rash is helpful but finding out what is causing it very important. Remember, you are not born with allergies; your immune system learned to be allergic to something over time. Usually your dermatologist can figure out the offending agent just by asking you some key questions. Sometimes, you may need a sample of the potential allergen placed on your skin under a little patch of adhesive tape. This process is called patch testing. Your dermatologist may actually place 20 to 80 samples on your back. This makes sense since most lotions have - long list of ingredients. The samples are placed on a Monday and then removed on Wednesday.  A final check of any reactions is done on Friday. It’s best not to get the patches wet or sweaty so don’t schedule hot yoga! Once the allergen is identified, your dermatologist will give you a detailed printout of the products you should avoid. 

Author
Snehal Amin, MD

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