The excimer laser targets a narrow beam of ultraviolent light onto skin. Now approved by the Food and Drug Administration for treatment of psoriasis, it can be useful in treating small, localized areas. For example, if there are only a few plaques of psoriasis (less than 10% of body affected) with not-too-thick scale, then this form of targeted light treatment can be very helpful.

Psoriasis has traditionally been treated with topical creams or ointments, ultraviolet light or, in severe cases, with medications taken by mouth. More recently, there are new and effective "biologics" that involve injection of substances that inactivate signals in skin that result in the red, scaly plaques of psoriasis.

Treatment with ultraviolet light usually involves standing in a "light box" where the whole body receives the ultraviolet light, not just the areas affected by psoriasis. Although ultraviolet light is helpful in treating psoriasis, it also increases the risk of skin cancer. The better treatment, therefore, would be to target the ultraviolet light only to the areas affected by psoriasis.

The excimer laser does this. The laser light is focused only on the plaques of psoriasis. Since normal skin is not affected, higher doses of ultraviolet light can be given. Side effects can include redness, blistering, and darkening of treated skin, all of which should go away with time. Although the treated patches of psoriasis may go away, they usually return in about six months.

This laser technology is relatively new. More clinical studies will help determine the best dose and frequency of laser treatments for psoriasis and the long-term effects of the treatment.

New discoveries about psoriasis are making possible a wide variety of treatments. If you have psoriasis, it is important to consult a doctor to find the best treatment for you.