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Updated June 29, 2015.

People have been using the sun to treat psoriasis and other skin diseases since the beginning of recorded history. Since the discovery of artificial ultraviolet light, physicians have also harnessed the power of light to treat skin disease. If you do not have significant psoriatic arthritis, light treatment can definitely be a good option to consider. It is generally safe, effective, and cost-efficient compared to many other psoriasis treatment options.


Many types of light have been used over the years to treat psoriasis. The most common type used today is narrow-band ultraviolet B (sometimes call narrow-band UVB). It is a stand up cabinet in the doctor’s office (home units are also available, as well as special units designed to treat only the hands or feet if only those areas are affected). Treatment is usually given three times a week to start, and then tapers down to once a week or less once the patient is clear.

The sequence of treatment is simple. The doctor determines whether phototherapy is right for you and sets up a treatment protocol. At each treatment session, you discuss your last treatment with the phototherapy technician to make sure there was no burning or other problems. Based on this information, he or she will input the settings for that day’s treatment.

The patient then enters the treatment room, removes his or her clothing (genitals must remain covered), puts on special glasses to protect the eyes, and then steps into the machine.

Some doctors also have the patient apply Vaseline-based lotion to the plaques being treated in order to increase light absorption. Length of treatment varies due to many factors, including previous treatments, skin color, and skin sensitivity and may last from less than a minute to over 10 minutes. Often, treatment time will increase slightly at each visit.

Light treatment will often begin to help in the first 3-4 weeks and help a lot by 2 months. Plaques will become thinner and scaling less noticeable. Since light treatment does not affect the internal organs or suppress the immune system, it is especially useful in populations where other drugs may cause problems, like children or pregnant women.

The main risks of light treatment are similar to those of getting too much sun, like burning or stinging. Some medications can make this problem worse, so it is important to tell your doctor's office about any new medications you start, including over the counter or prescription drugs. As with the sun, chronic use of light treatment over many years can increase your risk of skin cancer. That is why it is important to cover non-treated areas with a towel or sunscreen during treatment and have an annual skin check with a board-certified dermatologist. Eye protection is also important as repeated exposure without it can lead to eye damage.

Most people improve well with this treatment, but about 10% of people with psoriasis actually get worse with natural or artificial ultraviolet light, so it is important to have a physician monitoring your treatment.

Home units similar to those used in a doctor's office are also available, which can make light therapy more convenient. They do require some simple monitoring and maintenance. If you have been having good success with light treatment it is definitely worth discussing a home unit with your doctor. They come in many different sizes and price ranges, but usually cost at least several thousand dollars. Insurance will sometimes pay all or part of this cost.

Some people wonder if getting natural sun or going to a tanning bed is an alternative to light treatment in the doctor's office. Although both can help some, natural sun or tanning beds are both less effective and more dangerous than treatment with your doctor. That is because the narrow-band UVB machines are calibrated just with the wavelength of light that best helps psoriasis, allowing more improvement with less light used. Natural sun and tanning beds are also more difficult to monitor an exact dose of light, which can lead to more burns and less improvement. The National Psoriasis Foundation, along with the US Department of Health and Human Services and the World Health Organization, discourages the use of tanning beds.

Excimer laser is another common light-based treatment for psoriasis. It works similarly to light treatments described above but is more focused on specific spots instead of treating the whole body. It is especially useful for people with small but troublesome areas, like thick plaques of psoriasis on the elbows, hands, or scalp. Instead of ongoing maintenance treatment, most people get a course of excimer for 2 - 3 months and then stop once they are clear. As the psoriasis starts to recur (hopefully after 4 - 6 months of being clear), treatment is restarted. Although excimer laser has the same risks as light treatment, it only affects the treated areas so the risks are lower overall.

We are fortunate to have many new and exciting treatments for psoriasis. For many people, however, the tried and true option of light treatment still holds the best balance for risk, benefit, and cost. Not every dermatologist's office offers light or laser treatments, so contact clinics in your area to find out if it might be a good option for you.