Vivien Williams: Hand-washing is essential for preventing the spread of germs. But, sometimes, all this scrubbing can cause a rash. Does this mean you're allergic to the soap?

Dawn Davis, M.D., Dermatology, Mayo Clinic: One important thing to differentiate from allergic contact dermatitis is irritant contact dermatitis.

Vivien Williams: Dr. Dawn Davis says allergic contact dermatitis means a substance is causing an allergic reaction on your skin. But irritant contact dermatitis means your skin is inflamed from repeated exposure to something.

Dr. Davis: If I used lye soap on my skin, and I used it over and over again, I would develop an irritant contact dermatitis simply from eroding away the natural barrier of my skin with repetitive washing.

Vivien Williams: Dr. Davis says it's not always easy to tell the difference between an allergy or irritant.

Dr. Davis: So it's very helpful to go to a health provider, especially a dermatologist, to help differentiate between irritant contact dermatitis

Vivien Williams: and an allergy. That way you can properly treat the rash and prevent it from happening again.

For the Mayo Clinic News Network, I'm Vivien Williams.