Things to know about light therapy for psoriasis

Things to know about light therapy for psoriasis

Light therapy, or phototherapy, can improve psoriasis symptoms in many individuals. Light therapy works by reducing skin inflammation and slowing out skin cell development.

If a person has moderate to severe psoriasis, or psoriasis that has not reacted to other therapies, physicians may prescribe light therapy.

However, light therapy has side effects, in addition to its advantages. Repeated and long-term exposure to light therapy can increase the risk of skin cancer in a person.

In this post, we look closely at light therapy for psoriasis, including its forms, effectiveness and potential side effects.

What is light therapy for psoriasis?

Light therapy can treat psoriasis
Light therapy can treat psoriasis but will not cure it.

Light therapy includes shining ultraviolet light (UV) on the skin, which can minimize plaque size, itchiness and appearance. It may even completely clear them out.

Light therapy does not cure psoriasis but it can enable people to manage their disease and improve the quality of their lives.

Light psoriasis therapy works by reducing the excess growth of skin cells, which prevents the development of plaques. It also limits skin cell growth by affecting DNA function.

Light therapy procedure

Based on the areas that the psoriasis affects, a person may get phototherapy in one area, such as the hands or scalp, or throughout their entire body. A health care professional must cover sensitive areas of the skin during surgery, such as the eyes and genitals.

Light therapy requires multiple sessions to increase the amount of time the skin is exposed to UV light slowly, and to give it time to recover.

People usually undergo three to five hours of light therapy per week over the course of 2–3 months. Depending on the type of light therapy, people usually see an difference within 2–4 weeks.

The skin of every person reacts differently to phototherapy, both in how much improvement they see in their symptoms of psoriasis and how long those benefits last. The mean time of remission is 3–12 months.

Due to the increased risk of skin cancer, doctors are urging people to limit their use of psoralen and ultraviolet A (PUVA) phototherapy to 150 sessions for life.

Is light therapy effective?

Light therapy is effective in reducing or eradicating the psoriasis symptoms.

An estimated 75% of people who use the most common type of ultraviolet B (UVB) narrow-band therapy should develop clear skin. That will last for a minimum of 6 months.

Research has found that treatments with narrow-band UVB are effective against a rarer form of psoriasis called acute guttate psoriasis, and that people have been happy with the procedure.

According to the Health Care Center for Quality and Efficiency, using light therapy to treat psoriasis results in noticeable improvement or a total reduction of symptoms in 50–90 per cent of people.

Types of light therapy

psoriasis therapy machine
The best method of phototherapy would depend on which parts of the body influence the psoriasis.

There are many different ways to deliver psoriasis light therapy including different kinds of light and equipment.

A health care professional should choose a type of phototherapy to use, based on the following factors:

  • how much of the body the psoriasis affects
  • which body parts psoriasis affects
  • how much psoriasis affects an individual’s quality of life
  • a person’s overall health
  • a person’s skin type

One significant difference between the different forms of phototherapy is the type of UV light used in the treatment:

  • UVA has a long wavelength. It can go through glass windows and penetrate to deeper levels of the skin. People must use UVA treatments in combination with psoralen, which makes the skin more receptive to the UVA rays.
  • UVB has a shorter wavelength. It only reaches the upper levels of the skin and does not require psoralen.

The different types of light therapy for psoriasis include:

  • Narrow-band UVB. Narrow-band phototherapy, the most common light therapy, limits the light wavelengths used in treatment to 311–313 nanometers, to keep possible side effects in check.
  • Broad-band UVB. Broad-band phototherapy is the oldest form of light therapy for psoriasis. It uses a wider wavelength than narrow-band therapy.
  • Laser UVB. Laser techniques use a smaller, more targeted beam of UVB. Healthcare professionals prefer this technique when psoriasis affects less than 5 percent of the body.
  • Topical PUVA. With PUVA, a person either soaks in a bath or applies a lotion containing psoralen, which makes the skin more receptive to the UV light treatment that follows.
  • Oral PUVA. With oral PUVA, a person takes pills containing psoralen before phototherapy. This form of treatment may be especially helpful for very thick plaques.
  • Pulsed dye laser (PDL). Healthcare professionals most often use PDL for small lesions on the surface of the skin or nail psoriasis.
  • Balneophototherapy. Here, a person will undergo UV light treatments either while bathing in a salt-based solution or immediately afterward.
  • Low-level light or laser therapy. Sometimes called “cold laser” treatment, doctors also recommend this treatment for other forms of inflammation and chronic pain.
  • UVB phototherapy at home. Physicians may prescribe at-home follow-up treatment, with individuals using hand-held or smaller-scale light boxes to stay on top of their psoriasis and manage any increases in itchiness and plaques, or “flares.”

Who should get light therapy?

If creams and lotions are not enough to manage psoriasis symptoms, a doctor or skin specialist, called a dermatologist, may prescribe light therapy.

Light-therapy can benefit people with moderate to severe psoriasis. The condition affects 3–10 percent of the body in mild psoriasis while extreme psoriasis affects more than 10 per cent of the body.

People who take drugs and supplements over- the-counter that make their skin more sensitive to UV rays should not undergo phototherapy.

These photosensitizing medications include:

  • antihistamines
  • contraceptives
  • diuretics
  • sulfa drugs

Speak to a healthcare professional before deciding on phototherapy about any existing medicines or medications.

Pregnant women should avoid mild psoriasis treatment, as should those with:

  • a history of skin cancers, both melanoma and non-melanoma
  • a depressed immune system
  • lupus
  • known photosensitivity issues

Side effects of light therapy

When planning a phototherapy course a health care professional should recognize a person’s sensitivity to UV light. Despite this precaution, there are still side effects people may experience.

Possible side effects of light therapy include:

  • mild sunburn, which typically is not serious and is possible to resolve by changing the UV dosage
  • a stinging or itching sensation
  • an increased likelihood of cold sores in people prone to them
  • signs of premature aging of the skin, such as dark spots and loose or leathery skin
  • blisters
  • an increased risk of skin cancer


There is no cure for psoriasis but people can monitor their symptoms and improve their quality of life with medication.

Phototherapy can be of tremendous help to people with moderate to severe psoriasis.

Because of the potential for an increased risk of skin cancer, people receiving intensive phototherapy treatment should have their skin regularly tested by a doctor.


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