Light therapy, also called phototherapy, is a treatment for psoriasis that consists of exposure to specific wavelengths of light. Light therapy is an effective treatment for moderate to severe psoriasis. Between 50 percent and 90 percent of people with psoriasis who undergo light therapy experience noticeable improvement to their symptoms. In some cases, the symptoms go away entirely.

“I'm already in my second month of light therapy. I've got a cabin at home so that's great!” wrote a MyPsoriasisTeam member. “This therapy really helps me and I'm almost completely ‘clean’... :-)”

Unlike tanning beds, phototherapy delivers certain wavelengths — measured in nanometers — that are therapeutic for psoriasis, while reducing the emission of wavelengths that cause melanomas and other forms of skin cancer. Full-body light therapy can be used to treat psoriasis that affects the whole body. Targeted phototherapy — such as excimer laser therapy — can help treat plaque psoriasis on specific areas in the body. And unlike traditional or biologic systemic therapies, light therapy does not suppress the body's immune system.

Types of Light Therapy

Several types of light therapy that have been developed and used for the treatment of psoriasis over the last few decades.

UVB Light

The first light therapy consisted of broadband ultraviolet light B (UVB) (290–320 nanometers). This type of light was later replaced by narrowband UVB light (311-313 nanometers) when researchers found that it was more effective. According to the National Psoriasis Foundation, narrowband UVB light requires fewer treatments per week than broadband UVB light. UVB therapy involves exposing the skin to a light source under the guidance of a medical professional on a regular treatment schedule.

Home UVB phototherapy can be a convenient and cost-effective choice for people living with psoriasis. Like phototherapy in a health care provider’s or doctor’s office or clinic, home phototherapy requires a consistent treatment schedule.

Excimer Laser

The excimer laser (308 nanometers) was invented in 1997 and has been approved by the U.S. Food and Drug Administration. Along with narrowband-UVB light, the excimer laser represents a first-line therapy for plaque psoriasis. Excimer laser is used as a targeted light therapy and can spare body areas that do not need therapy, minimizing side effects like skin irritation and burning as well as the long-term risk of skin cancer on unaffected skin. Healthy skin can be further protected by applying sunscreen with a sun protection factor (or SPF) level of at least 50.

PUVA

Another conventional therapy is psoralen — a drug that is activated by light — plus ultraviolet A light (PUVA). In PUVA therapy, psoralen may be given orally or via injection, or applied directly on the skin. PUVA is currently the second-line therapy for plaque psoriasis. Read more about PUVA treatment for psoriasis.

Balneophototherapy

Balneophototherapy is another light-therapy treatment. In balneophototherapy, people bathe in warm water containing salt for about 20 minutes while being exposed to ultraviolet light while bathing or immediately afterwards.

Side Effects of Light Therapy

Light therapy is associated with certain side effects. For example, excimer light therapy may cause blisters and a burning sensation. Other types of light therapy may cause short-term side effects including:

• Edema (puffiness or swelling caused by fluid trapped in body tissues)
• Pain
• Itching
• Crusting
• Lesions
• Skin hemorrhages

The main long-term side effects of light therapy include:

• Pigmentation
• Photoaging (premature aging of the skin)
• Cataracts
• Increased risk of skin cancer

PUVA is associated with a higher risk of skin cancer than narrowband UVB, according to some research. If you are currently undergoing light therapy, it is important to be checked regularly by your dermatologist.

Before initiating treatment, talk with your health care provider if you have an intolerance to light or are taking drugs that increase your sensitivity to light, such as sulfonamides, fluoroquinolones, coal tar, and tazarotene. Pregnant women and people with cerebrovascular diseases or malignant skin conditions should not receive phototherapy.

Limitations of Light Therapy

According to a report published in the Journal of the American Academy of Dermatology, the use of light therapy at U.S. clinics is declining, likely due to factors such as cost and time commitment, increased use of home light therapy, and increased awareness of skin cancer risk.

Light therapy can be expensive because of equipment maintenance and calibration, staff time, and facility space requirements. These costs may not be fully covered by Medicare and private health insurance. The time demand involved may be a deterrent, as well. To be effective, light-therapy treatment can last between four weeks and three months, and is usually administered three times per week.

A MyPsoriasisTeam member shared that light therapy helps their psoriasis but noted how time-intensive the treatment can be. “Once you stop the light treatment your psoriasis can return and often does,” they wrote. “I found over time that if I kept up a maintenance schedule with the light treatment then I could hold the flares at bay for a much longer period of time, i.e., I do the six to eight week light treatment until I am clear and up to the maximum time in the UVB chamber, then I drop back to once (or even twice) a week just to keep the psoriasis calm.”

What About Sunlight for Psoriasis?

Even though sunlight contains both UVB and UVA light, UVB works best for psoriasis. UVB from the sun works the same way as UVB in light-therapy treatments.

However, using sunlight to treat psoriasis is not as effective and not recommended for everyone. Some topical treatments, such as tazarotene and coal tar, increase the risk of sunburn. Additionally, people who are using PUVA or other forms of light therapy should avoid or limit exposure to natural sunlight and protect themselves with sunglasses, clothing, and sunscreen.

What About Tanning Beds for Psoriasis?

Some people use indoor tanning beds as an alternative to natural sunlight, but these machines primarily use UVA light, not the more beneficial UVB light. The National Psoriasis Foundation does not support the use of tanning beds as a substitute for light therapy performed under a health care provider’s supervision. Read more about tanning beds and psoriasis.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriasis and their loved ones. On MyPsoriasisTeam, more than 90,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

Are you using light therapy for your psoriasis? Share your experience in the comments below or start a conversation by posting on MyPsoriasisTeam.