National Psoriasis Foundation
About psoriasis

Symptoms and diagnosis

Psoriasis is an autoimmune disease that causes raised, red, scaly patches to appear on the skin. It typically affects the outside of the elbows, knees or scalp, though it can appear on any location. Some people report that psoriasis is itchy, burns and stings.

If you develop a rash that doesn't go away with an over-the-counter medication, you should consider contacting your doctor.


About 95 percent of the time, your health care provider can make a psoriasis diagnosis just by visual inspection. Your doctor will consider where the raised, red, scales appear, if they have well-defined edges and how the rash responds to medication when making a diagnosis.

Psoriasis may seem similar to eczema, but there are several differences:

  • Psoriasis plaques are well-defined; eczema tends to be flatter with less well-defined edges.
  • Eczema typically occurs on locations atypical for psoriasis, such as the front of elbows or behind the knees. Psoriasis is most often found on the outside of knees and elbows, the scalp, the lower back, the face, the palms and soles of feet. It also can show up in other places, such as fingernails, toenails, the genitals and inside the mouth.

When biopsied, psoriasis skin looks thicker and inflamed when compared to skin with eczema.

Your doctor also will want to learn about your family history. About one-third of people with psoriasis have a family member with the disease, according to dermatologist Dr. Paul Yamauchi with the Dermatology and Skin Care Institute in Santa Monica, Calif.

Need to find a provider?

Search our health care provider directory »