Doctors use UV light therapy to treat various common skin conditions, such as psoriasis and eczema. They consider it effective and safe, although it may cause short- and long-term side effects, including itching and wrinkling.

UV light therapy is not safe for everyone, such as people with a history of skin cancer or those with fair skin who develop sunburn easily.

This article examines UV light therapy, including its uses, types, side effects, and the conditions for which it is unsafe. It also discusses devices that provide therapy at home and what to expect from sessions in a clinic.

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UV light therapy — also called phototherapy — involves the administration of UV radiation to treat various skin conditions. The radiation is a form of energy that scientists measure on a scale called the electromagnetic (EM) spectrum. UV radiation is the portion of the EM spectrum between visible light and X-rays.

Doctors consider the therapy safe and effective for specific uses. It plays a major role in dermatology, the field of medicine that treats skin conditions. The most frequent uses include:

  • Psoriasis: This is an autoimmune condition that accelerates the growth cycle of skin cells. Autoimmune means a person’s immune system attacks their own tissues. Psoriasis is the most common use of the therapy.
  • Long-term or chronic eczema: Eczema — also called atopic dermatitis — is an inflammatory skin condition. The therapy may be effective for certain types of eczema when other treatments do not produce satisfactory results or are inappropriate.
  • Mycosis fungoides: This is a condition where T-cell lymphocytes — a type of white blood cell — become cancerous and affect the skin. The therapy can cause inflammation in the early stages, but it subsides without needing to stop treatment sessions.
  • Vitiligo: This is an autoimmune condition where patches of skin lose pigment. When cases do not respond to topical treatment, UV light therapy is frequently a second-line treatment choice. Topical refers to the application of creams that contain medication to the skin.
  • Generalized lichen planus: This is an inflammatory autoimmune condition that affects the skin. Doctors consider UV light therapy a good option when people do not respond to systemic immunosuppressive therapy, medications that tamp down the immune system.
  • Polymorphic light eruption: This condition causes a rash in response to exposure to sunlight. UV light therapy is effective but can produce a rash in 50% of individuals. However, this is manageable with the use of topical medications.
  • Cutaneous graft-versus-host disease: This skin condition may occur in response to a type of stem cell transplant. It responds to some types of UV light therapy.

Some forms of UV light therapy include:

UVB light therapy

UVB light has a short wavelength that reaches the top layer of the skin. It suppresses DNA synthesis, which decreases inflammation. DNA is the genetic code in every cell. The mechanism of action for UVB light therapy is unclear but involves many processes.

Generally, UVB light therapy has many properties, such as:

  • anti-inflammatory
  • cytotoxic, meaning it causes damage to cells
  • immunosuppressive, meaning it reduces immune system activity

This is available in broadband — 270–350 nanometers (nm) — and narrow band (NB-UVB) — 311–312 nm. A doctor or dermatologist will tailor the type for a person’s skin and condition.

The excimer laser is also a type of UVB light therapy that works well for vitiligo and other skin conditions.

Doctors increasingly use NB-UVB as it involves shorter exposure and treatment duration and leads to more extended remission periods. It is a common treatment for psoriasis, vitiligo, and eczema.

UVA light therapy

UVA light therapy has a longer wavelength that penetrates the middle layer of the skin. UVA decreases cell turnover and has an immunosuppressive effect on the skin.

UVA1 refers to the wavelength that ranges from 340–400 nm. UVA1 treats various skin conditions, including eczema and cutaneous T-cell lymphoma (CTCL).

PUVA light therapy

PUVA is a combination of UVA light and psoralens. Psoralens are compounds in plants that produce temporary skin sensitivity to UVA.

Doctors use PUVA light therapy to treat several skin conditions, including psoriasis, vitiligo, and CTCL. However, it is a less favorable treatment than UVB, as older research shows that over 350 doses of PUVA have associations with an increased risk of squamous cell carcinoma, a type of skin cancer. Many experts advocate for less than 150 doses to minimize risk.


Heliotherapy entails exposure to natural sunlight, the UV part of which produces beneficial effects in small doses. These include:

  • inducing the production of vitamin D and other protective chemicals
  • suppressing immunity
  • reducing inflammation
  • inhibiting cell growth, which helps curtail the growth of tumors

This UV light therapy type can treat psoriasis, eczema, and other skin conditions.

Home UV light therapy is a relatively safe and effective self-treatment for certain skin conditions. An experienced doctor should supervise someone using these types of home devices, but not all dermatologists consent to do this due to the potential for side effects.

Some devices that deliver UV light therapy involve walk-in units for the whole body. Other devices entail tabletop or hand-held models for spot treatment.

Evidence from 2021 suggests that home treatment has downsides, such as difficulty managing session duration and equipment. A lack of cost reimbursement from health insurers is an additional issue.

A 2022 review notes that the short-term effects of UV light therapy include:

  • itching
  • atypical dryness
  • blistering
  • increased pigmentation
  • light-induced inflammation of parts of the eye
  • photoconjunctivitis, which occurs due to inflammation in the conjunctiva — a membrane that covers the eyelids and the whites of the eyes — following UV exposure
  • photokeratitis, which occurs due to UV exposure to the eye

Long-term side effects entail various light-induced skin cancers and light-induced aging. The latter effects involve:

  • wrinkling
  • atypical dryness
  • freckling
  • dilation — or widening — of tiny blood vessels in the skin
  • loss of elasticity

Cataracts is another concern — a condition that causes clouding in the lens of the eye. This is why eye protection is mandatory for light treatment.

UV light therapy is not safe for everyone. Research findings indicate that people with the following conditions should avoid it:

  • Systemic diseases that involve increased sensitivity to light: Systemic diseases affect the entire body, not only the skin. One example is lupus, an autoimmune condition affecting the skin and many other body parts.
  • Skin conditions that entail increased sensitivity to light: An example is xeroderma pigmentosum, which causes a defect in the enzyme system that repairs DNA following damage induced by UV rays.
  • History of skin cancer: This is particularly important in melanoma, a type of cancer in the skin cells that make a pigment called melanin.

Additionally, experts do not advise phototherapy for people who:

  • have Fitzpatrick skin types 1 and 2 — referring to people with fair skin who develop sunburn easily with sunlight exposure
  • take immunosuppressive medications — these drugs can decrease the strength of the immune system
  • use photosensitizing medications and creams — drugs that can increase sensitivity to light
  • are pregnant or nursing
  • are unable to stand unassisted for less than 10 minutes
  • have a history of excessive exposure to natural sunlight or UV light therapy

The length and frequency of treatment sessions depend on the type of light therapy and the condition:

  • UVB: Most people have three sessions per week. The initial session may take less than 5 minutes and may gradually increase to a maximum of 30 minutes per session.
  • UVA1: UVA1 treatment involves five sessions per week, usually for 3–4 weeks.
  • PUVA: The number and duration can vary with different skin conditions.
  • Heliotherapy: There are different methods. One type entails two sessions per day. It may start with 10–20 minutes per session and gradually increase to 3–6 hours of exposure per day. Treatment can occur for a duration of 3–4 weeks.

Improvements also differ with the type and condition. For example, guttate psoriasis — a variant of psoriasis — responds very well to UVB therapy. Some individuals notice them after a few treatments, while others do not experience them until after considerably more treatments.

UV light therapy generally can dry out the skin, so home care may involve using a fragrance-free moisturizer.

UV light therapy is a major dermatology treatment for various skin conditions, such as psoriasis, eczema, and vitiligo. Some different types include UVB, UVA, PUVA, and heliotherapy.

A person may undergo therapy at home, but it is important to have a doctor’s supervision. Short-term side effects may involve itching and increased pigmentation, while long-term side effects may entail wrinkling and loss of elasticity.

The doctor overseeing a person’s care can advise on the required number of sessions. The length of time necessary to experience improvements varies depending on the skin condition and the type of therapy a person has.

UV light therapy is not safe for certain people, including those with skin conditions that cause increased sensitivity to light.