Many people with psoriasis use light therapy to help clear up hard-to-treat patches of skin, as well as larger areas of the body affected by the condition. Light therapy, or phototherapy, is an option when topical treatments alone don’t work. People like it because it can clear up psoriasis for as long as six to 12 months. Ultraviolet B The standard light therapy devices use ultraviolet B (UVB) rays, which are also found in natural sunlight. When exposed to the skin, UVB rays slow the abnormally rapid turnover of skin cells that constitutes psoriasis. One of the drawbacks to UVB therapy is that it takes multiple trips to the doctor’s office, sometimes twice a week or more for several weeks. Some treatment sessions can last several hours, and it takes about 30 or more treatments for skin to clear. When patches return, you can begin light therapy again. Lasers Lasers are also a go-to option for people with psoriasis. Two lasers used for light therapy are the excimer laser and the pulsed dye laser. During treatment with a pulsed dye laser, your skin may feel like it’s being snapped by a rubber band. Laser treatments may require fewer doctor visits than UVB therapy to clear up psoriasis. PUVA If more than 10 percent of your body is affected by psoriasis, psoralen and ultraviolet A therapy (PUVA) may be for you. During this treatment, doctors combine ultraviolet light with a medicine called psoralen, which makes the skin more sensitive to light. For moderate cases, it takes about 25 treatments to clear psoriasis, which is less than other light therapies. While PUVA can be very effective for treating psoriasis, it can have side effects, including skin cancers. Considering light therapy? If you have a weak immune system, light therapy may be a good option because it doesn’t reduce your body’s ability to fight disease like some other psoriasis treatments. It’s also safe if you’re a woman who is pregnant or wants to get pregnant. Because light therapy uses ultraviolet light, it may not be the best choice if you have a higher than average risk for skin cancer. However, sunscreen may be used on unaffected areas to reduce the risk. Tip: If you’re thinking about light therapy, you’ll want to tell your doctor about all of the medicines, herbs, and vitamins you take. Some can make you more sensitive to light. At-Home treatments If your skin responds to light therapy in the doctor’s office, you may be a candidate for a light therapy device that your doctor prescribes for use at home. Most people like home therapy because it’s more convenient than going to the doctor’s office two or three times a week. And it’s just as safe and effective as office treatments, according to a study in the British Medical Journal. However, you’ll still need to see your doctor regularly. If your doctor says it’s OK, you also may want to try exposing your skin to natural sunlight for five to 10 minutes daily. Go out at noon, when the sun is strongest. Just be sure to wear sunscreen on areas unaffected by psoriasis. Try to be patient: It can take several weeks or longer before you notice any changes in your skin.