Psoriasis treatment with light therapy involves exposure of natural ultraviolet light from the sun and controlled delivery of artificial ultraviolet light. It is important that light therapy to treat psoriasis be administered by a doctor, since spending time in the sun or a tanning bed can cause skin damage and can increase the risk of skin cancer. There are several forms of light therapy to treat psoriasis.
First, psoriasis treatment with sunlight. 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, non-burning exposure to sunlight clears or improves psoriasis in many people. Therefore, exposing affected skin to sunlight is one initial treatment for the disease.
Second, psoriasis treatment with 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 to treat psoriasis 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 is is less effective than PUVA treatment. 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 for psoriasis is not without risk. It can cause more severe and longer lasting burns than broadband treatment.
Third, psoralen and ultraviolet A phototherapy (PUVA). This phototherapy psoriasis 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 ten percent of the skin is affected or when the disease interferes with a person’s occupation. Compared with broadband UVB treatment for psoriasis, 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. 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, melonoma skin cancers. Simultaneous use of drugs that suppress the immune system, such as cyclosporine, have little beneficial effect and increase the risk of cancer.
Lastly, psoriasis light therapy combined with other therapies. Studies have shown that combining ultraviolet light treatment and a retinoid, like acitretin, adds to the effectiveness of UV light for the treatment of psoriasis. For this reason, if patients are not responding to light therapy, retinoids, may be added. UVB phototherapy, for example, may be combined with retinoids and other treatments for psoriasis. One combined therapy program, referred to as the Ingram regimen, involves a coal tar bath, UVB phototherapy, and application of an anthralin-salicylic acid paste that is left on the skin for six to twenty-four hours. A similar regimen, the Goeckerman treatment, combines coal tar ointment with UVB phototherapy. Also, PUVA can be combined with some oral medications (such as retinoids) to increase its effectiveness.