Light Therapy for Psoriasis

Phototherapy for Moderate to Severe Cases

Phototherapy, also known as UV light therapy, can effectively treat certain types of psoriasis. This treatment involves exposing the skin to controlled amounts of ultraviolet (UV) radiation similar to that from the sun. It may be prescribed when conservative therapies fail to provide relief for moderate to severe psoriasis.

A man's hands in a phototherapy booth

 Science Photo Library / Getty Images

Side effects tend to be mild. In addition to psoriasis, phototherapy may also be used to treat eczema, vitiligo, lichen planus, and cutaneous T-cell lymphoma.

This article discusses the different types of UV light therapy for psoriasis, the potential risks of phototherapy, and more.

What Is Phototherapy?

Phototherapy, also known as light therapy, is a type of treatment that uses certain types of ultraviolet (UV) light to improve a health condition.

It has been known for centuries that sunlight can improve many inflammatory skin conditions, including psoriasis and atopic dermatitis. UV radiation has immunosuppressive and anti-inflammatory effects that can help temper the inflammation that drives many of these diseases.

The sun gives off electromagnetic energy in various forms. Of these, UV radiation is the type that has a shorter wavelength and more energy than the visible light. There are two types used in phototherapy:

  • UVA radiation, which has a wavelength closest to that of visible light
  • UVB radiation, which has a shorter wavelength and slightly more energy than UVA radiation

Types of Phototherapy for Psoriasis

Beginning in the early 20th century, clinicians began to develop different types of phototherapy to help people with psoriasis. Today there are several modalities used to treat the disease, including:

Although limited exposure to the sun can be beneficial to the skin, phototherapy is preferred for moderate to severe psoriasis since the UV radiation can be dosed and controlled. As such, phototherapy for psoriasis can be very effective. Skin clearance rates are reported to be in the 60% to 70% range following initial phase therapy.


Broadband ultraviolet B (BB-UVB) was the first type of phototherapy to be developed. It involves exposing the skin to wavelengths of light between 290 and 313 nanometers (nm). Years later, researchers developed a kind of UVB therapy that uses smaller wavelengths (between 308 and 313 nm). That is why it is called "narrow band."

Narrowband ultraviolet B (NB-UVB) is the most common type of phototherapy used today, for several reasons:

  • It is more effective than BB-UVB.
  • It can be used for a variety of different skin conditions.
  • It is easier to use than other forms of phototherapy.
  • It has fewer side effects compared to BB-UVB or PUVA.

Both BB-UVB and NB-UVB therapy can benefit from the application of coal tar to the skin. The procedure, referred to as Goeckerman therapy, appears to enhance the effects of phototherapy.


Psoralen plus ultraviolet A (PUVA), the second-most common form of phototherapy, is performed in two parts. First, you will be given a topical or oral compound, called psoralen, to sensitize your skin to the UVA radiation. Depending on your condition, you will either take a pill or have a topical formulation applied to your skin. Psoralen can also be applied topically by soaking in water that contains the medication.

Because UVA radiation is not as strong as UVB, you need this extra boost to make the therapy effective.

Laser Excimer Therapy

A newer and less commonly used form of phototherapy is called laser excimer therapy. It is a form of UVB-NB therapy in which the beam of light is narrowed to target smaller areas of skin. The lasers deliver higher doses of radiation, which can help treat the skin more quickly.

Laser excimer therapy is approved by the U.S. Food and Drug Administration for mild to moderate psoriasis.

Side effects are typically mild, but it might hurt a bit for some people. Treated areas may have bruising, sunburns, and possibly scarring.

What Is LED Light Therapy?

LED (light-emitting diode) therapy uses lights of different wavelengths to treat a variety of skin conditions, including acne, eczema, and psoriasis. Unlike other types of phototherapy, this type of treatment doesn't use ultraviolet (UV) radiation. Also, LED light therapy devices are available without a prescription.

Research shows that certain wavelengths of visible light may work against plaque psoriasis. One 2012 study published in Journal of the European Academy of Dermatology and Venereology found blue light and red light therapy to be effective in treating the condition. The Food and Drug Administration has since approved a wearable, blue-light device for treating mild psoriasis at home.


Studies show that phototherapy can effectively treat:

  • Areas of thick plaque psoriasis that are resistant to topical treatments
  • Psoriasis on the hands or feet
  • Nail psoriasis
  • Scalp psoriasis

However, phototherapy is rarely used on its own. It is generally recommended when topical therapies, such as corticosteroids, are unable to provide relief.

Phototherapy can be used to enhance the effects of topical therapies. For moderate to severe psoriasis, phototherapy is often used with oral or injectable drugs that temper inflammation from within. These include:

  • Disease-modifying antirheumatic drugs (DMARDs) like methotrexate or cyclosporine
  • Newer generation biologics like Humira (adalimumab), Enbrel (etanercept), or Remicade (infliximab)

Phototherapy is often an attractive option, since it is cost-effective, has few side effects, and can be used during pregnancy, unlike some other psoriasis treatments.

Risks and Contraindications

Most people do relatively well with phototherapy. However, it may cause side effects in some, including:

  • Sunburn-like reaction (mainly with UVB)
  • Itching
  • Mild stinging or burning
  • Dry skin
  • Dark spots (more common with darker skin types)
  • Blistering (rare)

Long-term side effects include:

  • Freckles
  • Premature skin aging (wrinkles, age spots, loss of skin tone)
  • Increased risk for skin cancer

Less commonly, psoralen used in PUVA phototherapy may cause nausea. Since PUVA is performed in a standing lightbox, protective eye goggles are needed to prevent cataracts that may develop as a result of the increased light sensitivity.

Skin Cancer Risk

A number of older studies suggested that phototherapy may increase the risk of skin cancer, particularly a type known as squamous cell cancer. The risk may be highest in people who get PUVA therapy over an extended period of time, although UVB therapy may also increase the risk. The current evidence, however, suggests the risk is extremely low.

According to a a 2015 review of studies published in the Journal of Psoriasis and Psoriatic Diseases, there is no clear evidence of an increased skin cancer risk associated with UVB phototherapy among all skin types.

To be on the safe side, healthcare providers recommend that you have regular skin screenings to check for any pre-cancerous lesions. If you have concerns about cancer, don’t hesitate to discuss them with your dermatologist in advance of your treatment.

UV radiation used for phototherapy should not be confused with the ionizing radiation used for X-rays. UV radiation mimics sunlight, while high-energy ionizing radiation can damage the DNA in cells, potentially causing cancer.


Despite the benefits of phototherapy, it may not be a good option for you if you:

  • Have a history of a photosensitivity disorder
  • Take photosensitizing medications
  • Have a history of melanoma
  • Have lupus or severe liver or kidney disease
  • Are immunosuppressed

People with fair skin may also need to be cautious as they are more likely to experience irritation.

Before Phototherapy

Before the phototherapy session is even scheduled, your dermatologist will determine if it is safe for you. To do this, they will perform a head-to-toe examination of your skin and ask whether you have a family history of skin cancer or photosensitizing disorders.

You will also want to advise your healthcare provider about any and all drugs and supplements you are taking. This includes patches, creams, and over-the-counter remedies. Some medications, such as retinoids, certain antibiotics, and chemotherapy drugs, can make your skin more sensitive to UV light.

If you are having PUVA therapy, you may be asked to see an ophthalmologist to have an eye exam before you begin.


The length of treatment can vary by the type of phototherapy used, the severity of symptoms, the amount of skin involved, and what type of photosensitizing agent is used.

With respect to the actual procedure, the first light therapy treatment may last only a few seconds. Over time, the sessions will increase based on your skin type, your tolerance to treatment, and the strength of the light used. Treatments rarely last longer than a few minutes.

Several treatments are usually required each week:

  • BB-UVB may require three to five treatments each week.
  • NB-UVB requires two to three treatments per week.
  • PUVA generally requires 25 treatments over two to three months.
  • Laser excimer therapy is usually given twice weekly and requires fewer treatments.

Treatments generally continue until your skin is clear. Maintenance treatments are sometimes needed to prevent acute flares.


Phototherapy is typically done in a dermatologist’s office in a 5 x 7-foot lightbox. Newer handheld devices are also available for spot treatments, while full-body lamps and lightboxes can treat the hands and feet. Home phototherapy units are also available and are typically used for maintenance.

What to Wear

No special clothing is needed for your appointment, but you may want to bring older clothes if your healthcare provider plans to use coal tar. Coal tar not only smells but can stain your clothes if you happen to get some on your hands.

If your arms are being treated, a lightweight, long-sleeved shirt may help prevent sun exposure on the way home. Soft socks and a pair of open-toe sandals can do the same if your feet are sore or sunburned after treatment.

Cost and Health Insurance

The cost of phototherapy can vary by your location and the type of procedure performed. Health insurance may cover some of the cost of treatment, but almost invariably requires prior authorization.

Check with your insurance company to find if phototherapy is covered in your schedule of benefits and what your copay or coinsurance costs will be.

What to Bring

Be sure to bring your ID and insurance card to the appointment as well as an accepted form of payment for copayment or out-of-pocket costs.

If coal tar is being used, you may want to bring a nailbrush and some deodorant to help minimize the smell. A moisturizing cream can also help. You should also bring sunscreen, sunglasses, and a hat to reduce sun exposure when outdoors, especially if psoralen is used.

During Phototherapy

When you arrive, you will be asked to sign in and present a photo ID and insurance card. Once completed, you will be escorted to a changing room and asked to remove any clothes that cover the skin being treated. Areas that do not need treatment should be covered and protected as much as possible.

If needed, you may be provided with the following protective tools:

  • Sunscreen to protect your neck, lips, and backs of the hands
  • Special glasses or goggles to protect your eyes
  • Sunscreen for nipples and areola in women
  • A covering for the male genitals

The nurse or phototherapy technician will be tasked with applying coal tar or topical psoralen to the affected skin, if needed. If oral psoralen is used, you will be asked to take it one to two hours before the procedure. If undergoing PUVA therapy to treat a large area of skin, you may be asked to soak in a bath of psoralen solution for several minutes.

Once prepared, you will either be taken to a lightbox for treatment or treated with a handheld device while standing or sitting. The actual procedure may induce a warm sensation similar to that of a mild sunburn.

Once the session is completed, you can shower or wash and change back into your clothes. The nurse or healthcare provider will then check the condition of your skin and recommend medication if you have any discomfort.

After Phototherapy

It is important to avoid natural sunlight after receiving phototherapy. This is especially true for the first 24 hours, when your skin will be most inflamed. Among some of the precautions to take:

  • Wear long-sleeved shirts, long pants, sunscreen (with zinc oxide and an SPF of 30 or higher on areas of skin that don't have psoriasis), sunglasses, and a hat when outdoors.
  • Take extra care to protect your eyes from the sun for the next 24 hours. This will help prevent cataracts after PUVA treatment.
  • Oral antihistamines and a topical hydrocortisone cream may help ease any itching.
  • Moisturize your skin with a fragrance-free moisturizer as often as needed, and at least once daily.

While skin redness and irritation are common after phototherapy, call your healthcare provider if you experience blisters, rash, burns, ulcers, drainage, or a fever of 100.4 degrees F or more.

Upon the completion of therapy, you'll typically schedule a follow-up with your dermatologist to evaluate your response and the need for maintenance therapy. You may also be asked to see your ophthalmologist for a follow-up examination of your eyes.

A Word From Verywell

Phototherapy is an age-old treatment with practical applications today. If your psoriasis is not under control with topical medications, ask your dermatologist whether phototherapy is an appropriate option for you. Never self-treat your condition with a home phototherapy unit unless given proper guidance by a dermatologist. Treating psoriasis inappropriately can actually make your condition worse. The same applies to the use of tanning beds and tanning lamps, both of which should be avoided without exception.

9 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

By Ruth Jessen Hickman, MD
Ruth Jessen Hickman, MD, is a freelance medical and health writer and published book author.