Phototherapy
Ultraviolet (UV) light from the sun causes the activated T cells in the skin to die, a process called apoptosis. Apoptosis reduces inflammation and slows the overproduction of skin cells that causes scaling. Daily, short, nonburning exposure to sunlight clears or improves psoriasis in many people. Therefore, sunlight may be included among initial treatments for the disease. A more controlled form of artificial light treatment may be used in mild psoriasis (UVB phototherapy) or in more severe or extensive psoriasis (psoralen and ultraviolet A [PUVA] therapy).UVB phototherapy--Some artificial sources of UVB light are similar to sunlight. Newer sources, called narrow-band UVB, emit the part of the ultraviolet spectrum band that is most helpful for psoriasis. Some physicians will start with UVB treatments instead of topical agents. UVB phototherapy is also used to treat widespread psoriasis and lesions that resist topical treatment. This type of phototherapy is normally administered in a doctor’s office by using a light panel or light box, although some patients can use UVB light boxes at home with a doctor’s guidance. Generally at least three treatments a week for 2 or 3 months are needed. UVB phototherapy may be combined with other treatments as well. One combined therapy program, referred to as the Ingram regime, involves a coal tar bath, UVB phototherapy, and application of an anthralin-salicylic acid paste, which is left on the skin for 6 to 24 hours. A similar regime, the Goeckerman treatment, involves application of coal tar ointment and UVB phototherapy. PUVA--This treatment combines oral or topical administration of a medicine called psoralen with exposure to ultraviolet A (UVA) light. Psoralen makes the body more sensitive to this light. PUVA is normally used when more than 10 percent of the skin is affected or when rapid clearing is required because the disease interferes with a person’s occupation (for example, when a model’s face or a carpenter’s hands are involved). Compared with UVB treatment, PUVA treatment taken two to three times a week clears psoriasis more consistently and in fewer treatments. However, it is associated with more short-term side effects, including nausea, headache, fatigue, burning, and itching. Long-term treatment is associated with an increased risk of squamous cell and melanoma skin cancers. PUVA can be combined with some oral medications (retinoids and hydroxyurea) to increase its effectiveness. Simultaneous use of drugs that suppress the immune system, such as cyclosporine, have little beneficial effect and increase the risk of cancer. In very rare cases, patients who must travel long distances for PUVA treatments may, with a physician’s close supervision, be taught to administer this treatment at home.
