Mild psoriasis: light therapy/phototherapy

Light therapy or phototherapy involves exposing the skin to ultraviolet light under medical supervision. Treatments usually take place in a doctor’s office or psoriasis clinic or outdoors with sunlight. The key to success with light therapy is consistency.

Excimer laser

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 two brands currently on the market are the Xtrac and the Xtrac Velocity.

The excimer laser can target select areas of the skin affected by mild to moderate psoriasis. 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.

Sunlight

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.

Tanning beds

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.  

The American Academy of Dermatology, the FDA and the Centers for Disease Control and Prevention all discourage the use of tanning beds and sun lamps. The ultraviolet radiation from these devices can damage the skin, cause premature aging and increase the risk of skin cancer.

Most practicing dermatologists discourage psoriasis patients from using tanning beds. However, some view this method as a last resort if patients do not have access to light therapy. Consult with your dermatologist before going to a tanning bed to treat your psoriasis.