This is cost-effective and it has been propagated as an effective way to treat psoriasis without medication. Decreases of PASI scores greater than 75% and remission for several months have commonly been observed. Side effects may be mild such as itchiness, folliculitis, sunburn, poikiloderma, and a theoretical risk of nonmelanoma cancer or melanoma has been suggested. Some studies indicate no increased risk of melanoma in the long term. Data are inconclusive with respect to nonmelanoma skin cancer risk, but support the idea that the therapy is associated with an increased risk of benign forms of sun-induced skin damage such as, but not limited to, actinic elastosis or liver spots. Dead Sea balneotherapy is also effective for psoriatic arthritis. Tentative evidence indicates that balneophototherapy, a combination of salt bathes and exposure to ultraviolet B-light (UVB), in chronic plaque psoriasis is better than UVB alone. UV phototherapy
Phototherapy in the form of sunlight has long been used for psoriasis. UVB wavelengths of 311–313 nanometers are most effective, and special lamps have been developed for this application. The exposure time should be controlled to avoid overexposure and burning of the skin. The UVB lamps should have a timer that turns off the lamp when the time ends. The amount of light used is determined by a persons skin type. Increased rates of cancer from treatment appear to be small. Narrowband UVB therapy has been demonstrated to have similar efficacy to psoralen and ultraviolet A phototherapy (PUVA).
A 2013 meta-analysis found no difference in efficacy between NB-UVB and PUVA in the treatment of psoriasis, but NB-UVB is usually more convenient.One of the problems with clinical phototherapy is the difficulty many people have gaining access to a facility. Indoor tanning resources are almost ubiquitous today and could be considered as a means for people to get UV exposure when dermatologist-provided phototherapy is not available. Indoor tanning is already used by many people as a treatment for psoriasis; one indoor facility reported that 50% of its clients were using the center for psoriasis treatment; another reported 36% were doing the same thing. However, a concern with the use of commercial tanning is that tanning beds that primarily emit UVA might not effectively treat psoriasis. One study found that plaque psoriasis is responsive to erythemogenic doses of either UVA or UVB, as exposure to either can cause dissipation of psoriatic plaques. It does require more energy to reach erythemogenic dosing with UVA.UV light therapies all have risks; tanning beds are no exception, being listed by the World Health Organization as carcinogens. Exposure to UV light is known to increase the risks of melanoma and squamous cell and basal cell carcinomas; younger people with psoriasis, particularly those under age 35, are at increased risk from melanoma from UV light treatment.