Q: I have had psoriasis on my legs and elbows for the past seven years. It is an ugly and embarrassingthing to have on your body. I have used prescribed cream, but the only thing that helps is the sun in the summer. What causes psoriasis? Would it help me to go to a tanning salon?
A: Psoriasis is a chronic skin disease, common among Caucasians in this country and thought to be transmitted genetically. The disorder is caused by an excessive growth of cells in the outer skin layer (epidermis), but no one is sure why these cells form at such a rapid rate.
Psoriasis causes skin damage (lesions) anywhere on the body, but favors elbows and knees where skin is stretched and flexed. Psoriasis may also "pit" fingernails and create joint pain in the fingers and lower spine.
A number of creams and ointments are effective in controlling psoriatic lesions in many patients. Many have shared your experience of improvement on exposure to sunlight. In fact, exposure to ultraviolet light, often coupled with the application of ointments, is a common and very effective therapy.
I would not recommend that you go to a tanning parlor where there is no control of the amount of exposure to ultraviolet light. Instead, you should seek such treatment from a dermatologist who may also combine light treatment with a pill (psoralen) that increases the sensitivity of skin to the wavelength of ultraviolet // light that is used.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine and associate dean for faculty affairs at the school.