Dermatologists have an array of therapies to treat psoriasis. Steroid and moisturizing creams can often clear up mild psoriasis cases, while potent drugs like methotrexate and biologic agents, which affect the immune system, tackle more stubborn and widespread plaques.
Phototherapy is another treatment option if topical treatments are insufficient or you can’t or won’t use systemic drugs because of their risks, side effects, or expense. According to new clinical guidelines from the American Academy of Dermatology and the National Psoriasis Foundation, published online in July 2019 in the Journal of the American Academy of Dermatology, phototherapy is a safe and effective treatment alternative for moderate to severe psoriasis.
How phototherapy works
Phototherapy exposes your skin to ultraviolet (UV) light—the same kind of radiation that comes from the sun. In psoriasis, an immune system malfunction causes cells in the upper layer of your skin to reproduce too quickly. UV rays penetrate your skin to slow the cells’ growth and reduce inflammation.
Patients who have mild to moderate psoriasis can also use phototherapy as an add-on (adjunct) treatment to topicals, as can patients for whom systemic drugs haven’t adequately controlled their more severe psoriasis. Several modalities of phototherapy are available.
Ultraviolet B phototherapy
Dermatologists use UVB phototherapy as an adjunct or stand-alone treatment when psoriasis covers more than 5 percent of the body—it’s effective, safe, easy to use, and relatively inexpensive. UVB phototherapy exposes the skin to either narrowband (NB-UVB) or broadband (BB-UVB) wavelengths. NB-UVB is more effective in clearing plaque psoriasis and has largely replaced BB-UVB. It’s estimated that NB-UVB is effective in clearing skin in about 60 to 70 percent of patients.
Typically, you’ll undergo NB-UVB two to three times a week until your disease goes into remission. It can take two to three months to achieve results, so patience and consistent treatment are key to its success.
Adding a drug like methotrexate, a retinoid, or a biologic will help clear skin faster with a lower dose of light. After your skin has cleared, you’ll need maintenance therapy about once a week. Remission length varies from six months to two years.
Phototherapy is usually administered at a dermatologist’s office or a clinic. During the treatment, UV rays are briefly emitted as you stand naked in a light box. Phototherapy can also be delivered via an excimer laser, which precisely targets smaller or hard-to-penetrate areas such as the elbows, knees, palms, soles of the feet, and scalp. The laser clears plaques faster than traditional phototherapy.
You can purchase a special light box or handheld device to use at home. A home unit requires a doctor’s prescription and costs about $3,000, a portion of which Medicare and some health insurers typically cover. Research finds that home treatment works just as well as phototherapy delivered in a doctor’s office, and patients tend to be highly satisfied with its effectiveness and convenience.
Psoralen + UVA
Psoralen + UVA, or PUVA, uses UVA rays, which are stronger than UVB rays, combined with psoralen, a light-sensitizing drug, administered either in pill form or as a bath mixture. PUVA works best for plaque psoriasis, guttate psoriasis (small, red spots that appear most often on the trunk and limbs), and psoriasis on the palms and soles of the feet.
Study results comparing the effectiveness of PUVA and UVB phototherapies have been mixed. However, dermatologists usually choose UVB for its convenience and lower risk of adverse effects.
Risks and side effects of phototherapy
Phototherapy can sometimes cause side effects such as redness, mild stinging or burning, itching, skin darkening, and less commonly, Blisterata and burns during the course of treatment. Long-term effects include premature aging of the skin and an increased risk for skin cancer. PUVA can increase cataract risk.
If you’re considering phototherapy, review the benefits and risks with your doctor. Also consider whether insurance will cover your treatments, and if you’re able to follow the two-to-three-times-weekly treatment schedule.