If the medicine you put on your skin isn't doing all that it needs to, your doctor may suggest adding phototherapy to your psoriasis treatment. It uses ultraviolet rays that come from sunshine, artificial lamps, or lasers to slow skin cell growth and ease your symptoms.
Types of Phototherapy
Sunlight. Too many rays coming directly from the sun can make your symptoms worse and raise your chances of getting skin cancer. If your doctor tells you to get some sun each day, about 20 minutes a day should be enough. Use a sunscreen with zinc oxide and an SPF of 30 or higher on areas of your skin that don't have psoriasis.
UVB (ultraviolet B). Your doctor can treat you with UVB rays from a phototherapy machine in their office. You can also get one to use at home. But the lamps can give off ultraviolet A (UVA) rays. Both UVA and UVB rays are linked to skin cancer. Talk to your doctor about how to protect yourself from the cancer risk while being treated.
There are 2 main types of UVB treatments:
- UVB broadband: Your health care provider may use it to treat single patches, widespread psoriasis, and psoriasis that doesn't improve with topical treatments. In the short term, side effects might include redness, itching, and dry skin. Moisturizing regularly can help ease your discomfort.
- UVB narrowband: Many scientists and doctors think this type of UVB is more effective than broadband. But you may notice more serious burns from the treatments that last longer. Narrowband UVB lightbulbs release a smaller range of ultraviolet light. The treatment seems to work more quickly and keep psoriasis flares away for longer. And it often requires fewer treatments per week.
You'll probably need phototherapy treatments 3 days a week for 2 to 3 months. Your doctor might suggest you use UVB treatment along with another kind of therapy, like a cream made from coal tar. They may call this the Goeckerman regimen. Another combination treatment pairs anthralin-salicylic acid paste with ultraviolet light. You might hear this called the Ingram regimen.
There are also “targeted” phototherapy options that are able to concentrate treatment on smaller areas, like individual lesions on the skin. Some of the devices used in these treatments are made with lasers (see laser section below), but there are also non-laser machines that deliver targeted phototherapy.
Targeted therapies may be good for small, hard-to-reach areas on your skin. Ask your doctor if you’re a candidate for these targeted therapies.
PUVA (psoralen plus ultraviolet A). This treatment combines UVA lamp sessions with a drug called psoralen. You either take the drug as a pill or put it on your skin as a cream, lotion, gel, solution, or ointment. It makes your skin more sensitive to light. The process is called photochemotherapy. You'll probably go to your doctor's office 2 or 3 times a week for a total of 25 to 30 sessions.
PUVA clears up psoriasis quickly with long-lasting results. But using it for a long time can raise your chances of skin cancer. Because of that, it’s typically only recommended for severe cases or when other treatments haven't worked.
The treatment also has side effects such as:
- Burning and itching
Because psoralen makes your body extra sensitive to light, you need to protect your skin and eyes after taking it. Wear glasses that block ultraviolet light, and wear sunscreen for at least the first 24 hours after treatment.
Lasers. These highly focused beams of light target your psoriasis patches, not your healthy skin. This cuts down on side effects and may lower your chances of skin cancer. You'll also need fewer treatments compared with other types of light therapy.
The excimer laser uses focused, high-energy ultraviolet B light. It can help patches get better faster than other methods. You usually get this treatment in your doctor's office twice a week for 4 or 5 weeks.
Doctors also sometimes use pulsed dye lasers, or PDLs, to treat psoriasis. PDLs use a liquid with an organic dye to create a laser that delivers gentle bursts of focused light onto carefully targeted areas of skin. The heat that results clears away damaged blood vessels but keeps surrounding skin as safe as possible.
Side effects from laser therapy are generally mild, but some people say it can hurt a bit. You may also have bruising, sunburns, and possibly scarring at the spots that have been treated.
After laser treatment, you should stay out of sunlight and be careful not to injure the area. Call your doctor if you see blisters.
Home UVB phototherapy. There are units available for home use to deliver UVB phototherapy. As with all phototherapy treatments, these require a doctor’s prescription. When you use it, you need to keep a consistent treatment schedule as instructed by your doctor. Ask your doctor if you are a good candidate for one of these units.
Grenz rays. This approach is less common. Doctors give this treatment with “superficial X-ray machines” to deliver a form of soft X-rays that work in a way similar to UV light.
Photodynamic therapy. Though not common, your doctor may suggest photodynamic therapy for your psoriasis. This procedure uses special medicines that intensify the effects of a light source. Side effects of burned skin can limit the usefulness of this approach in the treatment of psoriasis. But scientists continue to study new versions of this treatment in search of better results.
Phototherapy in People of Color
In phototherapy, the light has to get through the top layer of skin -- the epidermis -- to get to the inflammatory cells that cause psoriasis. People with darker skin have more melanin in their skin. This makes it harder for light -- whether sunlight or artificial light -- to penetrate the skin.
As a result, a treatment session for someone with dark skin will typically last longer than for someone with lighter skin.
But each case is different, and there are other things to consider. For example, in some people with dark skin, psoriasis can show up as pinkish-red instead of brown. In these cases, your doctor might further adjust the exposure time of your treatment sessions, depending on the color of the psoriasis.
Dermatologists use special guides and tables to find the correct timing for each session.
If you use any kind of phototherapy, including natural sunlight, be careful not to get too much sun. Don't sun yourself in the yard or go out for a walk without sunscreen, for example. During an artificial light session, use sunscreen or wear clothes that cover up areas that don't need treatment.
Many things can make you more sensitive to light, like some blood pressure drugs, antibiotics, St. John's wort, and even celery. Stay away from these while you're getting phototherapy. And have regular skin exams to check for signs of skin cancer.