What Is Phototherapy?

Treatment for psoriasis, eczema, seasonal affective disorder, and more

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Phototherapy is a medical treatment in which natural or artificial light is used to improve a health condition. Treatment may involve ultraviolet (UV) fluorescent light bulbs, halogen lights, sunlight, or light-emitting diodes (LEDs).

Other names for phototherapy include light therapy and heliotherapy. The type of therapy you need and the way in which the light is used can vary depending on whether the phototherapy is for eczema, psoriasis, or other health conditions.

This article explains how light therapy is used to treat these conditions. It also discusses some of the risks involved.

what is phototherapy used for?

Verywell / Brianna Gilmartin

What Conditions Does Phototherapy Treat?

Phototherapy is used to treat skin conditions, certain types of cancer and precancer, and mood and sleep disorders. Specific health problems phototherapy can help include:

  • Barrett’s esophagus
  • Circadian rhythm disorders
  • Cutaneous T-cell lymphoma
  • Eczema
  • Endobronchial cancer
  • Esophageal cancer
  • Itchy skin
  • Newborn jaundice
  • Psoriasis
  • Seasonal affective disorder (SAD)
  • Sleep Disorders
  • Vitiligo

Types of Phototherapy

Phototherapy describes several different therapies that use light to treat health conditions. The type of phototherapy used depends on the reason for treatment and include:

  • Bili lights: A specific wavelength of fluorescent lights is used to treat newborn jaundice.
  • Bright light therapy: A lightbox that mimics natural sunlight is used to treat mood and sleep disorders.
  • Broadband UVB: Broadband UVB uses a wide range of ultraviolet-B rays. UVB rays are present in sunlight, but you can't see them.
  • Narrowband UVB: This involves using a smaller, more intense part of UVB to treat the skin condition. It’s the most common type of light therapy used today.
  • PUVA: Psoralen ultraviolet-A, or PUVA, combines UVA light with a chemical called psoralen, which comes from plants. Psoralen can be applied to your skin or you can take it as a pill. It makes your skin more sensitive to the light. 

PUVA has more side effects than some other light therapies. It's only used when other options haven't worked.

How Phototherapy Works

The way in which phototherapy works depends on the type of treatment and what it is being used to treat.

Phototherapy for Skin Conditions

Phototherapy treatment for skin conditions involves using ultraviolet (UV) light to slow skin cell growth and inflammation. Inflammation is one of the ways your immune system responds to infections, injuries, and foreign "invaders."

UVB rays affect the outermost layers of the skin. UVA rays are slightly less intense but penetrate more deeply into the skin. These two types of UV light can be used in different ways.

Skin conditions treated with phototherapy include:

  • Cutaneous T-cell lymphoma
  • Eczema
  • Itchy skin
  • Psoriasis
  • Vitiligo

The effects of light therapy for skin disorders are usually temporary. Phototherapy for skin conditions may take six to eight sessions and up to two months to work.

Phototherapy for skin conditions is generally considered safe. However, side effects include redness, dry or itchy skin, nausea (with PUVA), blisters, or folliculitis, an infection of the hair follicles. Long-term side effects include skin cancer and premature skin aging.

Phototherapy for Mood and Sleep Disorders

Bright light therapy is a type of phototherapy used to treat mood and sleep disorders. It involves using a lightbox—a specially designed box that emits a steady light that mimics sunlight.

Bright light therapy works by stimulating cells in the retina, which connects to the hypothalamus—the brain region that controls our circadian rhythms. 

Seasonal Affective Disorder (SAD)

Seasonal affective disorder (SAD) is a type of depression linked to certain seasons of the year. It usually begins in the fall and lasts through winter. Bright light therapy helps to relieve the symptoms of SAD.

Light therapy is an inexpensive and effective treatment with side effects that are mild and temporary.

If you take an antidepressant, light therapy may make it possible to lower the amount of medication you use. However, talk to your healthcare provider first before changing your antidepressant dose. Stopping your antidepressant has some health risks.

Phototherapy has also been explored for other kinds of depression. Some studies support it, but not all health experts agree that light therapy helps with depression.

Sleep Disorders

Your body has an inner "clock" that times your sleeping and waking cycles. It's known as your circadian rhythm, and it doesn't always work the way it should.

Light therapy can help those who have circadian rhythm sleep disorders such as delayed sleep phase syndrome (DSPS). People with DSPS often can't fall asleep until the wee hours of the morning or close to sunrise. Light therapy can help them shift to more normal sleeping times.

It's important to time the light therapy correctly. Your sleep specialist will help you plan the right time to use light based on your symptoms.

Phototherapy for Cancers and Precancers

Photodynamic therapy is the form of light therapy used to treat some kinds of cancer and precancers. It involves using a drug called a photosensitizer along with light.

Photosensitizers are applied to the skin. When light strikes the skin, it interacts with the drug to make a kind of oxygen that kills nearby cancer cells.

Photodynamic therapy is used to treat conditions such as:

  • Cancer of the esophagus, the tube that connects your mouth to your stomach
  • Endobronchial cancer, a type of lung cancer
  • Barrett's esophagus, a precancerous condition often caused by acid reflux

Photodynamic therapy is sometimes called photoradiation therapy or photochemotherapy.

Phototherapy has some advantages over treatments like radiation and chemotherapy. For example, it doesn’t usually have any long-term side effects. It leaves less scarring than surgery. And phototherapy costs a lot less than the other treatment options for cancer.

The downside is that it usually only works in areas on or just under the skin, where light can reach. It also does not help much with cancers that have spread.

Phototherapy for Newborn Jaundice

Bili lights are a type of phototherapy used to treat newborn hyperbilirubinemia and jaundice. These conditions cause a baby’s skin, eyes, and body tissues to turn yellow. The yellow color comes from too much bilirubin, a pigment made when red blood cells break down.

Light therapy lowers the baby’s bilirubin levels. It works by breaking down bilirubin so the baby's body can get rid of it properly.

There are two main ways to treat jaundice with light therapy. The usual way is to place the baby under halogen spotlights or fluorescent lamps. The baby's eyes are covered during the phototherapy treatment to protect against damage to the retinas.

Another technique is to use "biliblankets." The blankets have fiber-optic cables that shine blue light onto the baby's body. This method is most often used when babies are born early or when other treatments have already been tried.

Compact fluorescent lights and blue LED devices are also used to give babies phototherapy. They can be kept close to the body because they do not produce a lot of heat.

Light therapy for treating hyperbilirubinemia and jaundice is considered very safe. However, people sometimes have short-term side effects such as diarrhea, rashes, overheating, and water loss or dehydration.

Phototherapy Side Effects and Risks

Side effects and risks of phototherapy depend on the type of light therapy used.

Phototherapy for skin conditions carries the following risks:

  • Premature aging: UV rays can damage your skin cells. They can cause your skin to look and feel older more quickly. This premature aging of the skin is also known as photoaging.
  • Skin cancer: Some older studies found that being exposed to high amounts of artificial UV light raised the risk of skin cancer. Newer studies have found that PUVA may increase skin cancer risks, while narrowband UVB treatment poses no extra skin cancer risk.
  • Suppressed immune system: If you have light therapy often, it can suppress your immune system, leaving your body more open to diseases, infections, and skin cancers.
  • Vision problems: PUVA treatments for skin or photodynamic therapy for cancer can make your eyes more sensitive to light. Sensitivity can lead to eye damage if you are exposed to sunlight or other bright lights. Light therapy may also cause you to develop cataracts.

Bright light therapy for mood disorders also has a number of side effects you should be aware of. They include:

  • Headaches
  • Fatigue or tiredness
  • Insomnia
  • Hyperactivity
  • Irritability

Bili light therapy can cause dehydration. Newborns undergoing treatment for jaundice may be given IV fluids.

Who Should Avoid Phototherapy?

People with certain health conditions may need to avoid light therapy. Make sure your healthcare provider knows about your condition if you:

  • Are pregnant or breastfeeding
  • Have a family history of skin cancer
  • Have liver disease
  • Have lupus


Light therapy can be used to treat skin conditions, mood disorders, sleep disorders, some cancers, and jaundice in babies. Some treatments involve exposure to natural or artificial light. Others combine light therapy with a drug that makes the light more effective.

While light therapy is considered safe, some people do have side effects. And it's not right for everyone. If you're pregnant or nursing, have a family history of skin cancer, or have liver disease or lupus, light therapy might not be helpful.

15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Nankervis H, Thomas KS, Delamere FM, Barbarot S, Rogers NK, Williams HC. Phototherapy treatment. In: Scoping Systematic Review of Treatments for Eczema. Southampton, UK: NIHR Journals Library; 2016.

By Tolu Ajiboye
Tolu Ajiboye is a health writer who works with medical, wellness, biotech, and other healthcare technology companies.