Light therapy for psoriasis : What you should know

Light therapy, or phototherapy, may relieve many people’s symptoms of psoriasis. By reducing skin inflammation and slowing the development of skin cells, light therapy works.

When a person has moderate to serious psoriasis, or psoriasis that has not responded to other therapies, doctors may prescribe light therapy.

However, even with its advantages, light therapy has side effects. Repeated and long-term light therapy exposure may increase the risk of skin cancer in an individual.

We take a close look at light therapy for psoriasis in this article, including its forms, efficacy, and potential side effects.


A lady using light therapy
Light therapy can treat psoriasis but will not cure it.

Shining ultraviolet (UV) light on the skin requires light therapy, which may reduce the size, itchiness, and appearance of plaques. It may even clear them up completely.

Psoriasis is not healed by light therapy, but it can help people control their condition and increase their quality of life.

Psoriasis light therapy works by slowing down the excess growth of skin cells, which prevents the development of plaque. By influencing the functioning of the DNA, it also restricts the growth of skin cells.


An individual may receive phototherapy in one area, such as the hands or scalp, or across their entire body, depending on which areas the psoriasis affects. Before treatment, a healthcare professional will safeguard delicate skin areas, such as the eyes and genitals.

To gradually increase the amount of time the skin is exposed to UV light, and to give it time to recover, light therapy requires several sessions.

Over the course of 2–3 months, people typically attend three to five light therapy sessions a week. Depending on the form of light therapy, people usually see a difference in 2–4 weeks.

The skin of every individual responds differently to phototherapy, both in how much change they see in their symptoms of psoriasis and in how long those advantages last. 3-12 months is the average remission period.

Physicians advise individuals to limit their lifelong use of psoralen and ultraviolet A (PUVA) phototherapy to 150 sessions due to the increased risk of skin cancer.

Is light therapy effective?

In order to reduce or clear up the symptoms of psoriasis, light therapy is effective.

An approximate 75% of people would grow clear skin using narrow-band ultraviolet B (UVB) therapy, which is the most common form. This will last for 6 months at least.

Research has shown that narrow-band UVB therapies are successful against an uncommon type of psoriasis called acute psoriasis of the guttate, and that this therapy has satisfied individuals.

Using light therapy to treat psoriasis results in significant change or a total reduction of symptoms in 50-90 percent of individuals, according to the Institute for Consistency and Efficiency in Health Care.


There are several different methods, including various forms of light and equipment, to provide light therapy for psoriasis.

Based on the following considerations, a healthcare practitioner will choose which phototherapy method to use:

  • 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 main distinction between the different types of phototherapy is the type of UV light used in treatment:

  • UVA has a wavelength which is long. It can go through windows of glass and penetrate the skin to deeper levels. In conjunction with psoralen, people must use UVA therapy, which makes the skin more receptive to UVA rays.
  • UVB has a wavelength that is shorter. 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 physician or skin specialist, called a dermatologist, can prescribe light therapy.

Light therapy can help people with moderate to serious psoriasis. For mild psoriasis, 3-10% of the body is affected by the disease, while more than 10% of the body is affected by extreme psoriasis.

Phototherapy should not be done on people who take drugs and over-the-counter supplements that make their skin more sensitive to UV radiation.

Such photo-sensitizing drugs include:

  • antihistamines
  • contraceptives
  • diuretics
  • sulfa drugs

Before committing to phototherapy, speak to a healthcare provider about your existing supplements or drugs.

Light therapy for psoriasis should be avoided by pregnant women, as should people with:

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

Side effects

When preparing a phototherapy course, a healthcare professional will consider a person’s sensitivity to UV light. Notwithstanding this precaution, individuals can nevertheless experience side effects.

Possible light therapy side effects include:

  • Mild sunburn, which is normally not serious and can be resolved by changing the UV dosage
  • A stinging feeling or scratching sensation
  • An improved risk of cold sores in people vulnerable to them
  • Signs of premature skin ageing, such as dark spots and skin that is loose or leathery
  • blisters
  • an increased risk of skin cancer


There is no cure for psoriasis, but individuals are able to manage their symptoms and improve their quality of life through medication.

For people who have mild to serious psoriasis, phototherapy may be extremely beneficial.

Because of the potential for a higher risk of skin cancer, people receiving prolonged care with phototherapy should have their skin checked by a doctor on a regular basis.

About the author

Ray John