Phototherapy or light therapy, involves exposing the skin to ultraviolet light on a regular basis and under medical supervision. Treatments are done in a doctor's office or psoriasis clinic or at home with phototherapy unit. The key to success with light therapy is consistency.
National Psoriasis Foundation does not support the use of indoor tanning beds as a substitute for phototherapy performed with a prescription and under a doctor's supervision. Indoor tanning raises the risk of melanoma by 59 percent, according to the American Academy of Dermatology and the World Health Organization, and does not provide the type of light that most effectively treats psoriasis. Read more on the Psoriasis Foundation position on indoor tanning beds »
Find a provider who offers phototherapy in our Health Care Provider Directory »
Learn about different types of light therapy.
Ultraviolet light B (UVB)
Present in natural sunlight, ultraviolet B (UVB) is an effective treatment for psoriasis. UVB penetrates the skin and slows the growth of affected skin cells. Treatment involves exposing the skin to an artificial UVB light source for a set length of time on a regular schedule. This treatment is administered in a medical setting or at home.
There are two types of UVB treatment, broad band and narrow band. The major difference between them is that narrow band UVB light bulbs release a smaller range of ultraviolet light. Narrow-band UVB is similar to broad-band UVB in many ways. Several studies indicate that narrow-band UVB clears psoriasis faster and produces longer remissions than broad-band UVB. It also may be effective with fewer treatments per week than broad-band UVB.
During UVB treatment, your psoriasis may worsen temporarily before improving. The skin may redden and itch from exposure to the UVB light. To avoid further irritation, the amount of UVB administered may need to be reduced. Occasionally, temporary flares occur with low-level doses of UVB. These reactions tend to resolve with continued treatment.
UVB can be combined with other topical and/or systemic agents to enhance efficacy, but some of these may increase photosensitivity and burning, or shorten remission. Combining UVB with systemic therapies may increase efficacy dramatically and allow for lower doses of the systemic medication to be used.
Home UVB phototherapy
Treating psoriasis with a UVB light unit at home is an economical and convenient choice for many people. Like phototherapy in a clinic, it requires a consistent treatment schedule. Individuals are treated initially at a medical facility and then begin using a light unit at home.
It is critical when doing phototherapy at home to follow a doctor's instructions and continue with regular check-ups. Home phototherapy is a medical treatment that requires monitoring by a health care professional.
All phototherapy treatments, including purchase of equipment for home use, require a prescription. Some insurance companies will cover the cost of home UVB equipment. Vendors of home phototherapy equipment often will assist you in working with your insurance company to purchase a unit.
Although both UVB and ultraviolet light A (UVA) are found in sunlight, UVB works best for psoriasis. UVB from the sun works the same way as UVB in phototherapy treatments.
Short, multiple exposures to sunlight are recommended. Start with five to 10 minutes of noontime sun daily. Gradually increase exposure time by 30 seconds if the skin tolerates it. To get the most from the sun, all affected areas should receive equal and adequate exposure. Remember to wear sunscreen on areas of your skin unaffected by psoriasis.
Avoid overexposure and sunburn. It can take several weeks to see improvement. Have your doctor check you regularly for sun damage.
Some topical medications can increase the risk of sunburn. These include tazarotene, coal tar, Elidel (pimecrolimus) and Protopic (tacrolimus). Individuals using these products should talk with a doctor before going in the sun.
People who are using PUVA or other forms of light therapy should limit or avoid exposure to natural sunlight unless directed by a doctor.
Psoralen + UVA (PUVA)
Like UVB, ultraviolet light A (UVA) is present in sunlight. Unlike UVB, UVA is relatively ineffective unless used with a light-sensitizing medication psoralen, which is administered topically or orally. This process, called PUVA, slows down excessive skin cell growth and can clear psoriasis symptoms for varying periods of time. Stable plaque psoriasis, guttate psoriasis, and psoriasis of the palms and soles are most responsive to PUVA treatment.
The most common short-term side effects of PUVA are nausea, itching and redness of the skin. Drinking milk or ginger ale, taking ginger supplements or eating while taking oral psoralen may prevent nausea. Antihistamines, baths with colloidal oatmeal products or application of topical products with capsaicin may help relieve itching. Swelling of the legs from standing during PUVA treatment may be relieved by wearing support hose.
The excimer laser—recently approved by the Food and Drug Administration (FDA) for treating chronic, localized psoriasis plaques—emits a high-intensity beam of ultraviolet light B (UVB).
The excimer laser can target select areas of the skin affected by mild to moderate psoriasis, and research indicates it is a particularly effective treatment for scalp psoriasis. Researchers at the University of Utah, for example, reported in The Journal of Drugs in Dermatology that in a small series of patients, laser treatment, combined with a topical steroid, cleared scalp psoriasis that resisted other treatment.
Individual response to the treatment varies. It can take an average of four to 10 sessions to see results, depending on the particular case of psoriasis. It is recommended that patients receive two treatments per week, with a minimum of 48 hours between treatments.
There is not yet enough long-term data to indicate how long the improvement will last following a course of laser therapy.
Pulsed dye laser
Like the excimer laser, the pulsed dye laser is approved for treating chronic, localized plaques. Using a dye and different wavelength of light than the excimer laser or other UVB-based treatments, pulsed dye lasers destroy the tiny blood vessels that contribute to the formation of psoriasis lesions.
Treatment consists of 15- to 30-minute sessions every three weeks. For patients who respond, it normally takes about four to six sessions to clear the target lesion.
The most common side effect is bruising after treatment, for up to 10 days. There is a small risk of scarring.
Some people visit tanning salons as an alternative to natural sunlight. Tanning beds in commercial salons emit mostly UVA light, not UVB. The beneficial effect for psoriasis is attributed primarily to UVB light. National Psoriasis Foundation does not support the use of indoor tanning beds as a substitute for phototherapy performed with a prescription and under a doctor's supervision. Read more on the Psoriasis Foundation position on indoor tanning beds »
The American Academy of Dermatology, the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention all discourage the use of tanning beds and sun lamps. Indoor tanning raises the risk of melanoma by 59 percent, according to the American Academy of Dermatology and the World Health Organization. In May 2014, the FDA reclassified sunlamps (which are used in tanning beds and booths) from Class I (low risk) to Class II (moderate risk) products. The FDA can exert more regulatory control over Class II products, according to a press release on the FDA website.
The ultraviolet radiation from these devices can damage the skin, cause premature aging and increase the risk of skin cancer.