“When ultraviolet light hits skin, it does all kinds of things,” says Steven Feldman, MD, PhD, a professor of dermatology at the Wake Forest University School of Medicine in Winston-Salem, N.C. Ultraviolet light kills the immune cells in the skin that contribute to psoriasis, and research suggests that UV light may also disrupt the faulty signals between immune cells and skin cells that lead to psoriasis lesions.
With relatively few side effects, phototherapy is an effectiveyet underusedtreatment, experts say. “Phototherapy is a great treatment to start with,” recommends Kathy Kavlick, RN, community outreach nurse for the Murdough Family Center for Psoriasis in Cleveland. “Some people get really good results from it.”
Types of phototherapy
Phototherapy is usually administered on an outpatient basis in a dermatologists office two to three times a week, using a walk-in light booth that looks like a tanning bed stood on end. Light boxes for home use are also available.
There are two main types of phototherapy:
- Ultraviolet B light (UVB), one of the components of sunlight, is especially effective for treating psoriasis. During the treatment patients are exposed to the light for just a few seconds at first, and the exposure time is gradually increased to several minutes per treatment. UVB treatment is sometimes administered with topical treatments such as coal tar, anthralin, or just mineral oil. A form of UVB light known as narrow-band (NB-UVB) has been shown to be even more effective than UVB, and is increasingly being used by dermatologists.
- Although not as potent as UVB, ultraviolet A light (UVA) is also used to treat psoriasis. UVA treatment generally takes longer than UVBexposure times can reach 15 to 20 minutesbut at these higher doses it is also effective in clearing lesions. UVA light is often combined with an oral medication known as psoralen (a treatment known as PUVA).