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Phototherapy (Psoriasis)

As the name suggests, this psoriasis treatment uses natural or artificial ultraviolet light. Medically supervised phototherapy is the preferred method of phototherapy as it minimizes the risk of skin cancer by controlling the type and amount of ultraviolet light. Forms of light therapy include the medically supervised use of ultraviolet A (UVA) or ultraviolet B (UVB) light. In any form, light treatment is only effective if you get short-exposure – burns and skin damage can worsen psoriasis symptoms.

Phototherapy requires repeated exposure of the skin to ultraviolet light using one of several techniques. The procedure is done under medical supervision and may be advised when topicals alone are not effective.

Light therapy or phototherapy works by reducing inflammation and slowing down the production of skin cells, which can improve symptoms of psoriasis in many people. Phototherapy is typically used when psoriasis is widespread or if topical treatments have been proven ineffective.

Phototherapy involves the use of ultraviolet light to treat psoriasis. There are multiple types of phototherapy available. It can vary from phototherapy delivered in a dermatologist’s office (narrow-band UVB phototherapy, broad-band UVB phototherapy, laser UVB phototherapy, PUVA phototherapy), to home phototherapy prescribed by a dermatologist. Your dermatologist can help determine which type of phototherapy may be most appropriate for your psoriasis and life situation.

To achieve success with phototherapy, consistency is key. Phototherapy can require a significant time commitment and thus may not be appropriate for everybody. Phototherapy sessions are typically prescribed 3 – 5 times per week, with improvement often being noticed in the first month.

A healthcare professional will take all the necessary steps to determine if phototherapy is the right treatment for you. Despite the many precautions, people may still experience side effects and complications. These may include:

  • Dry and itchy skin
  • Temporary red skin due to light exposure
  • Mild sunburn (which may be caused by an increase in dosage)
  • An increased likelihood of cold sores in people already prone to them
  • Premature aging such as wrinkles and dark spots
  • An increased risk of skin cancer


The following factors may increase the risk of complications: 

  • Pregnancy or nursing
  • Allergy to sunlight
  • Liver disease
  • History of skin cancer
  • Use of certain photosensitizing drugs

Psoralens UVA (PUVA) is not recommended during pregnancy.

UVB phototherapy is considered the safest treatment during pregnancy for widespread psoriasis not controlled with topical treatment.

Some medications can increase your sensitivity to light. If you are starting phototherapy or are on phototherapy and starting a new medication, be sure to ask your doctor or pharmacist if your medication can increase your sensitivity to light.

Phototherapy can be effective for reducing or clearing up symptoms of psoriasis for a significant length of time. To achieve success, consistency is key. Phototherapy can require a substantial time commitment and thus may not be appropriate for everybody. Treatment sessions are typically prescribed three to five times per week, with improvement often being noticed in the first month. More severe psoriasis may require more treatments.

Research has found that using phototherapy to treat psoriasis results in an obvious improvement or a complete reduction of symptoms in 50 – 90% of people. Phototherapy can’t cure psoriasis forever and spots may develop again over time. When this happens, you may need a new treatment cycle to target the affected areas again.

Overall, the therapeutic goal is to minimize side effects while maintaining control of psoriasis and maximizing quality of life.

Types of Phototherapy

Ultraviolet B (UVB) is a wavelength of light found in natural sunlight that is used in specific concentrations as a form of treatment for moderate-to-severe psoriasis. Doctors may recommend light therapy when a patient hasn’t responded to other forms of treatment. It involves exposing the skin to an artificial UVB light source set at a specific wavelength for a set length of time on a regular schedule, allowing it to penetrate the skin, reduce inflammation and slow the growth of affected skin cells.

The duration of treatment depends on a number of factors ranging from the severity of psoriasis to your skin type, if you have any other medical conditions and if you’re taking any medications that may make skin more sensitive. UVB treatment is typically given three to five times a week and can last anywhere from four weeks to three months. The initial dose may be given at low concentrations to allow the skin to adjust, and then gradually increased over time.

There are two different types of UVB therapy—broadband and narrowband. Broadband is the oldest form of phototherapy and uses a wider wavelength than narrowband. It is rarely used in treatment anymore.  Narrowband UVB uses a more specific or “narrow” range of wavelengths and has proven to be the more effective form of phototherapy. It can reach more specific areas of the body such as skin folds and may clear psoriasis faster with only a few treatments.

UVB treatment is offered in different ways, from full-body units to localized units as well as hand-held units. Treatments are usually administered at a health care provider’s office, clinic or at home with a phototherapy unit. If you are considering a home phototherapy unit, your dermatologist can help determine which option is most appropriate for your psoriasis and lifestyle. It’s important to speak with your dermatologist about potential sensitivities related to your medical history and other possible interactions (i.e., medications, other skin products, etc.).

UVB therapy can be used alone, with coal tar products (Goeckerman Treatment) or with dithranol applied to the skin (Ingram regimen).

Goeckerman Treatment is a specialized form of light therapy formulated in 1925 by dermatologist William H. Goeckerman and continues to be used today due to its efficacy and prolonged remission time. Standard treatment includes a combination of the use of UVB therapy and crude coal tar as an ointment, cream, lotion, etc. applied daily to the skin. It has been successfully used in some patients who have failed at biologic therapies. 

The Ingram regimen is a combination of the Goeckerman treatment in addition to topical anthralin paste, also known as dithranol, which is an antipsoriatic topical derived from wood tar. Anthralin can be found in a small percentage of ointments or creams and is generally used on thick, large plaques of psoriasis. This form of treatment is initiated at low concentrations for short periods, then gradually increases over time.

Psoralen and ultraviolet A light therapy (PUVA) treatment involves taking a light-sensitizing medication (psoralen) before exposure to UVA light. UVA has a longer wavelength than UVB and therefore penetrates to deeper levels of skin. PUVA treatment slows down excessive skin cell growth and can clear psoriasis symptoms. This more aggressive treatment is typically used for more severe cases of psoriasis.

There are a few different types of PUVA treatment—topical PUVA and oral PUVA. Oral involves taking Psoralen orally 45-60 minutes before exposing the skin to UVA. Topical PUVA involves the person applying a lotion containing Psoralen or less commonly, diluting the medication in bathtub water and soaking in it for a recommended amount of time before exposure to UVA. The amount of Psoralen required and the length of exposures depends on the patient’s weight and pigmentation. Oral PUVA is used less and less based on availability and also safety risks regarding skin cancer.

PUVA generally involves two or three treatments a week for a total of 15-30 treatments. Patients should begin to see a significant improvement in their psoriasis after 15 treatments, although it doesn’t work for everyone. Stable plaque psoriasis, guttate psoriasis and psoriasis of the hands and feet tend to be most responsive to PUVA treatment. Typically, after 30 treatments, a decision is made whether to continue treatment. PUVA therapy is often administered in a stand-up booth at a medical office or clinic.

Excimer or pulsed-dye lasers (PDL) can also be used to treat mild-to-moderate psoriasis. The laser light is aimed directly at psoriasis plaques and never touches the surrounding skin, reducing the risk of UV radiation exposure. Excimer lasers use controlled UVB light whereas pulsed-dye lasers kill tiny blood vessels that are thought to contribute to psoriasis patches. Pulsed-dye lasers are most commonly used for small lesions on the skin or nail psoriasis.

If you are considering a home phototherapy unit, your dermatologist can help determine which type of home phototherapy may be most appropriate for your psoriasis and life situation. It would also be important to discuss any potential sensitivities that you may have related to your own medical history and other possible medications or products that you use.

Some private insurance plans may cover home phototherapy units, though public plans generally do not. It is best to check what coverage you may have if you are considering a home phototherapy unit. Phototherapy equipment is currently listed as an allowable  Medical Expense Tax Credit under the Income Tax Act (see Canada Revenue Agency’s list of common medical expenses).

Last updated October, 2022