Doctors generally treat psoriasis in steps based on the severity of the disease, size of the areas involved, type of psoriasis, and the patient's response to initial treatments. This is sometimes called the "1-2-3" approach. In step 1, medicines are applied to the skin (topical treatment). Step 2 uses light treatments (phototherapy). Step 3 involves taking medicines by mouth or injection that treat the whole immune system (called systemic therapy).

Over time, affected skin can become resistant to treatment, especially when topical corticosteroids are used. Also, a treatment that works very well in one person may have little effect in another. Thus, doctors often use a trial-and-error approach to find a treatment that works, and they may switch treatments periodtopically (for example, every 12 to 24 months) if a treatment does not work or if adverse reactions occur.

Light Therapy
Natural ultraviolet light from the sun and controlled delivery of artificial ultraviolet light are used in treating psoriasis.

o Sunlight--Much of sunlight is composed of bands of different wavelengths of ultraviolet (UV) light. When absorbed into the skin, UV light suppresses the process leading to disease, causing activated T cells in the skin to die. This process reduces inflammation and slows the turnover of skin cells that causes scaling. Daily, short, nonburning exposure to sunlight clears or improves psoriasis in many people. Therefore, exposing affected skin to sunlight is one initial treatment for the disease.

o Ultraviolet B (UVB) phototherapy--UVB is light with a short wavelength that is absorbed in the skin's epidermis. An artificial source can be used to treat mild and moderate psoriasis. Some physicians will start treating patients with UVB instead of topical agents. A UVB phototherapy, called broadband UVB, can be used for a few small lesions, to treat widespread psoriasis, or for lesions that resist topical treatment. This type of phototherapy is normally given in a doctor's office by using a light panel or light box. Some patients use UVB light boxes at home under a doctor's guidance.

A newer type of UVB, called narrowband UVB, emits the part of the ultraviolet light spectrum band that is most helpful for psoriasis. Narrowband UVB treatment is superior to broadband UVB, but it is less effective than PUVA treatment (see next paragraph). It is gaining in popularity because it does help and is more convenient than PUVA. At first, patients may require several treatments of narrowband UVB spaced close together to improve their skin. Once the skin has shown improvement, a maintenance treatment once each week may be all that is necessary. However, narrowband UVB treatment is not without risk. It can cause more severe and longer lasting burns than broadband treatment.

o Psoralen and ultraviolet A phototherapy (PUVA)--This treatment combines oral or topical administration of a medicine called psoralen with exposure to ultraviolet A (UVA) light. UVA has a long wavelength that penetrates deeper into the skin than UVB. Psoralen makes the skin more sensitive to this light. PUVA is normally used when more than 10 percent of the skin is affected or when the disease interferes with a person's occupation (for example, when a teacher's face or a salesperson's hands are involved). Compared with broadband 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 shortterm side effects, including nausea, headache, fatigue, burning, and itching. Care must be taken to avoid sunlight after ingesting psoralen to avoid severe sunburns, and the eyes must be protected for one to two days with UVA-absorbing glasses. Long-term treatment is associated with an increased risk of squamous-cell and, possibly, melanoma skin cancers. Simultaneous use of drugs that suppress the immune system, such as cyclosporine, have little beneficial effect and increase the risk of cancer.

Psoriasis: Topical Treatment

Psoriasis: Systemic Therapy