Before treatment - Patient with severe psoriasis	After treatment - The patient's dermatologist prescribed UVB phototherapy and an oral (taken by mouth) retinoid to clear this patient's psoriasis.
Photographs used with permission of the Journal of the American Academy of Dermatology.  All photographs were published in the Journal of the American Academy of Dermatology, Vol. # 45, Lebwohl M, Ali S. “Treatment of psoriasis. Part 1. Topical therapy and phototherapy,” 487-98; quiz 99-502. Copyright Elsevier (2001).

Number of treatments: UVB phototherapy requires time. To be effective, 2 to 5 treatments per week are given for several weeks. The exact number of treatments varies with the patient’s response, type of UVB phototherapy prescribed, and the severity of the psoriasis.

Some people need to pre-treat their skin. This can involve applying coal tar to the psoriasis the night before and washing it off in the morning. Before stepping into the light box, most people apply a thin layer of petroleum jelly or mineral oil to the psoriasis. This thin layer makes the UVB light more effective.

How long clearing lasts: Remission time varies. Recent studies suggest that it may be possible to increase clearing by continuing treatment for a bit after the skin clears. One such study found that more than half (55%) of the patients who did this were clear 1 year later. These patients received narrowband UVB phototherapy 3 times per week for 12 weeks. For the next 4 weeks, they received 2 UVB treatments per week. For the following 4 weeks, they received 1 UVB treatment per week.

Currently, most patients stop UVB phototherapy when their skin clears. Some begin the UVB treatments when the psoriasis starts to return.

Side effects: The skin may be red, itchy, or dry after UVB exposure. Some people develop a sunburn-like reaction and even blisters. Temporary worsening of the psoriasis also is possible before the skin starts to clear. Pregnant women may develop melasma, a skin condition that causes mottled skin.

Receiving years of UVB phototherapy may pose greater risks. Over time, exposure to UVB light may increase one’s risk of premature skin aging. Signs of premature skin aging include sagging skin, wrinkles, and dark marks. There also may be an increased risk of getting skin cancer. This is why sunscreen should be applied to all skin that does not require UVB phototherapy and a dermatologist must closely monitor all patients who receive phototherapy.