The UV Paradox: Why Dermatologists Use Light to Treat Psoriasis

Psoriasis runs in my family; though I haven’t struggled in the way that my father has, several years ago I had my first flare of psoriasis. I woke up one day and noticed scaly spots on my chest, elbows and knees. After trying prescription creams and feeling like they weren’t working fast enough, my frustration led me back to the tanning salon I’d sworn off years before. My skin always looked better in the summer, I had thought, so UV light must be the answer to this. As I got up from the tanning bed after my first session, I looked down at the places where I had psoriasis, and by some stroke of a miracle, they faded. Though my instincts were correct in treating my skin condition with UV light, doctors warn against simply sitting in the sun or climbing in a tanning bed in an effort to fade psoriasis. However, there are safe ways to use UV treatment to address the skin condition. Ahead, I spoke with dermatologists to get to the bottom of this treatment and how, under certain conditions, it can safely be used without damaging your skin.

Featured experts

• Dr. Shereen Teymour is a board-certified dermatologist in New York
• Jody A. Levine, MD is a board-certified dermatologist in New York

What is psoriasis?

“Psoriasis is an immune-related inflammatory condition in which immune signaling, particularly pathways involving T cells and cytokines, drives skin cells to proliferate much faster than normal,” explains New York dermatologist Dr. Shereen Teymour. This accelerated turnover, which is part of what creates the thick, scaly, itchy plaques associated with psoriasis.

How can UV light help with treating psoriasis?

Studies show that certain wavelengths of ultraviolet light can interrupt the process of accelerated skin cell turnover. “UVB light can help treat psoriasis by slowing down the overactive immune response in skin that causes inflammation,” explains New York dermatologist Jody A. Levine, MD.

Dr. Teymour further explains that UV light helps to decrease inflammatory immune activity in the skin, “which induces apoptosis of some of the activated immune cells contributing to psoriasis, and slows excessive proliferation of keratinocytes.” Essentially, a controlled dose of UV radiation can help quiet down both inflammation and abnormal skin cell turnover, in turn improving the appearance of plaques.

However, “The decision to use UV light will depend on factors including the severity and location of the psoriasis, the patient’s medical history, skin type and previous treatments,” says Dr. Levine.

How long does it take to see results?

With supervised narrowband UVB therapy, Dr. Teymour says that some patients may begin to see improvement after several weeks, but that a typical course of treatment often involves two to three sessions per week over several months. Substantial clearing occurs over roughly a six- to 12-week course of treatment. “The timeline varies depending on the severity of the psoriasis and how an individual responds to treatment,” says Dr. Teymour. Because psoriasis is a chronic condition, phototherapy can help control symptoms, but maintenance treatments may be needed.

Can using UV light for psoriasis be dangerous?

Rightfully so, the biggest concern is that general UV exposure can increase the risk of premature skin aging, sun damage and skin cancers, including melanoma and non-melanoma. “Tanning beds are especially concerning because they deliver high doses of UVA radiation and are not calibrated for psoriasis treatment,” explains Dr. Levine. “Medical phototherapy is different because the dose, wavelength and duration are carefully controlled to maximize benefit while minimizing risk.”

Dr. Teymour stresses that the operative word—controlled—is what makes the world of difference in utilizing UV light to treat the condition. “Medical phototherapy is very different from simply going out in the sun or using a tanning bed,” she says. Tanning beds generally emit UVA radiation predominantly, whereas UVB wavelengths are harnessed to treat psoriasis. The use of tanning beds to treat the condition is particularly concerning because they not only contribute to cumulative DNA damage, premature skin aging and hyperpigmentation, but they expose people to UV radiation without the precision or medical supervision of phototherapy. “With a medical phototherapy unit, we can precisely control the wavelength, dose and treatment schedule,” says Dr. Teymour.

Typically, narrowband UVB therapy is used and only a few wavelengths of UVB light between 311 to 313 nanometers (not the whole spectrum one is exposed to from the sun). “Still, patients undergoing phototherapy should be monitored by a dermatologist,” says Dr. Levine.

Dr. Levine notes that it’s important for patients to understand that not all light exposure is equal. “‘Getting sun’ or using a tanning bed is not a safe substitute for medical phototherapy. Psoriasis treatment should be individualized, and patients should work with a dermatologist to find an approach that addresses their specific symptoms and minimizes long-term risks,” she says. It’s also important to note that even legitimate medical phototherapy isn’t without risk. “Patients can develop erythema or burning, itching and dryness, and cumulative UV exposure, which is something to take into consideration,” says Dr. Teymour.