Morsani College of Medicine

Dermatology & Cutaneous Surgery

Allergic Contact Dermatitis

Are you itching to know what might be causing your skin rash?  If you have eczema or dermatitis, you might be allergic to something your skin has come in contact with.  Sometimes the allergen is fairly obvious, such as if you got exposed to poison ivy.  Many times however which chemical allergens are involved is not obvious.  Since avoidance of the allergens can often result in significant improvement or clearing of the rash, finding out what you might be allergic to is important.  The allergen testing process is called patch testing.  It is different from the scratch and prick testing that allergists do.

Patch testing involves having panels of allergens applied to the skin of your back and taped in place.  They are left in place for two days.  The tapes are then removed and a first reading is done.  A second reading is done a day or two later because the reaction is often delayed. During the patch testing process you cannot get your back wet.  After the second reading, you will receive a printout listing any allergens and what products would be safe to use. 

After you begin avoiding your allergens, the allergen you already have bound to your skin will slowly be shed, usually over 6 to 8 weeks, and you may begin to notice improvement or clearing of your dermatitis type rash. You will remain allergic to those allergens and will have to continue to avoid them.  For many people the relief obtained is significant and lasting.

by:Philip Shenefelt, MD

Dr. Shenefelt is Professor and Dermatologist at USF Health and actively see patients at the Morsani Center for Advanced Health Care on the USF campus and also at the USF Health Davis Island location. For appointments call 813-974-4744