Phototherapy or light therapy for psoriasis uses light, natural and artificial, to control psoriasis symptoms and prevent its complications. Light treatment cures the majority of the symptoms and is mainly used in the treatment of psoriasis, which is extensive.

Its use is widespread and is also indicated in the treatment of acne vulgaris, eczema, sleep disorders, some psychiatric disorders, and seasonal affective disorder (SAD).

However, the light therapy used for skin conditions is different from the one used for SAD, sleeping disorders, and other conditions. Light therapy is also referred to as heliotherapy.

UV light therapy, which includes UVB phototherapy and psoralen plus ultraviolet A (PUVA), is effective in controlling psoriasis symptoms.

More so when combined with topical treatment, light therapy is good to control symptoms of psoriasis of moderate to severe degree. It helps control the pain and itchiness of the lesions, which, go away. Do not use salicylic acid before light therapy because it lowers the efficacy of the therapy.

However, the treatment involves extensive work and several sessions per week. Additionally, the high risk of skin cancer due to long-term light therapy has to be borne in mind by the dermatologist when fixing the dosage regimen.

Sunlight is used as a natural phototherapy agent while artificial light sources, which are used, involve the use of artificial ultraviolet phototherapy lamps and are administered in a hospital or specialized centers by a dermatologist.

However, lightboxes and bulbs are available for prescribed home light therapy. It is important that you follow the advice of your treating doctor or dermatologist.

Dermatologists recommend light therapy for psoriasis because it can

  • Slow down the rapidly growing skin cells
  • Suppress the overly active immune system
  • Reduce inflammation of the skin
  • Reduce or stop the itching

Natural sunlight to cure psoriasis

The fact that patients with psoriasis find that their symptoms improve in summer when there is more exposure to the sun is not a coincidence.

Though too much sunlight is one of the trigger factors for a psoriasis flare, the right amount of exposure to sunlight can prove beneficial for psoriasis.

A dermatologist can assess the patient’s disease status and advise on the safest level of sunlight exposure.

Sunlight is made up of visible light rays and invisible ultraviolet and infrared rays. These rays are invisible because they have too short a wavelength for the eye to see. The particular wavelength of the ultraviolet rays makes it a good cure for psoriasis.

Ultraviolet rays again have different wavelengths. UVA rays are of longer wavelengths and can penetrate deeper into the skin. UVB rays are of shorter wavelengths and affect the outer layers of the skin.

How does sunlight act for psoriasis?

When skin psoriasis is exposed to the ultraviolet rays of natural sunlight or artificial sources, these rays penetrate the skin. As a result, the active T cells, which have migrated in large numbers to the skin, begin to die.

This reduces the excessive growth of the skin cells, which is seen to happen in psoriasis. Sunlight exposure results in decreased scales and inflammation of the skin, thus showing improvements in symptoms.

Mode of exposure

The psoriatic skin should be exposed to sunlight daily for brief periods at a time because excessive skin exposure to sunlight can worsen the psoriasis lesions and can also cause skin damage.

You could start with a five to ten-minute exposure and gradually increase by about 30 seconds each time.

All the affected areas should receive equal exposure for maximum benefits. You should protect the sensitive and normal areas of the skin, such as the face and hands by covering them with sunscreen.

It could take several weeks to see improvement. If you are using any topical application, consult your doctor before exposing yourself to the sun, because they can increase the risk of sunburn.

Do not use sunlight exposure for psoriasis improvement if you are taking light therapy.

Main types of phototherapy for psoriasis

There are three types of artificial means to give light treatment or phototherapy treatment for psoriasis.

  1. Broadband UVB phototherapy
  2. Narrowband UVB phototherapy
  3. PUVA

Artificial ultraviolet rays or UVB rays have been used for treating psoriasis since 1920.

UVB rays help modify the immune system, which is not working correctly in people with psoriasis. This helps in improving the symptoms.

Ultraviolet rays can be broadband or narrowband depending on the wavelength.

The UVA is the weaker form than the broadband UVB and both are used in different modes of light therapy for psoriasis.

These light rays are invisible to the eyes due to their wavelengths. It was in 1981 that the exact wavelength was discovered, which benefits psoriasis and it lies between 300-313nm.

As is known, ultraviolet rays are known to cause skin cancer. To minimize this risk, measured doses and modified treatment methods have been developed. You should always take light therapy under the guidance of a skilled practitioner.

1. Broadband Ultraviolet B (UVB) Phototherapy

Ultraviolet B or UVB therapy uses UV rays from an artificial source to manage psoriasis. This form of treatment is used in treating mild to moderate forms of guttate or plaque psoriasis ans is the most common type.

It can be used for skin psoriasis patches or widespread psoriasis as well as psoriasis, which has been resistant to topical psoriasis creams.

An estimated 75 percent of people using narrow-band ultraviolet B (UVB) therapy, will develop clear skin, which will last for at least 6 months.


A measured dose of the appropriate wavelength is given by means of specially designed fluorescent tubes, which are fitted into a cabinet so that the whole body is treated.

Alternatively, these tubes are also available in panels for localized treatment such as for hands or feet.


Each session takes only a few minutes and treatment is for two to three times a week for 6 to 8 weeks. At times, psoriasis may worsen after starting therapy. However, treatment should be continued and improvement will be seen

Short-term side effects include itching, redness, and dry skin, which can be treated by using a moisturizer.

2. Narrowband UVB Therapy

This is a newer form of UVB light treatment than broadband therapy with a better effect. As the name suggests, this is a finely tuned narrowed treatment to a wavelength band of 311nm.

You should know that the wavelength of light determines its effects such as light, warmth, and the capacity to burn the skin. Narrowing down the wavelength of light ensures the most benefits of treating psoriasis with faster and more prolonged effects.

The Narrowband does not contain the shorter wavelengths of sunlight, which cause harm to the skin. However, skin burns with narrowband UVB rays are seen to occur and can be long-lasting.


Treatment sessions with narrowband UVB are less than those with broadband. Narrow UVB is administered 2 to 3 times a week until the skin improves. After that, a maintenance dose of one sitting per week proves sufficient.

3. PUVA or Psoralen plus UVA (Ultraviolet A)

PUVA is a specialized treatment, which is also referred to as photochemotherapy as it combines treating psoriasis with phototherapy and a photosensitization drug. The light-sensitizing drug in PUVA is called psoralen.

Psoralen is given first before exposure to artificial UVA light. This is done because psoralen makes the skin psoriasis more responsive to UVA light, thereby allowing smaller doses of UVA to be required.

UVA light is used instead of UVB because UVA light penetrates deeper into the skin than UVB. This makes this treatment more aggressive and effective and also a better choice for more severe forms of psoriasis.

Other types of phototherapy

Other types of phototherapy that either aren’t as widely recommended, or widely used are described below.

1. Excimer Laser

Excimer laser involves targeting only the localized chronic psoriasis skin patches with a high-intensity beam of UVB rays. This leaves the surrounding normal skin unharmed. It is used for mild to moderate forms of psoriasis and its success rate varies. Due to the high intensity of the UVB beam, fewer treatment sessions are required.


Two treatment sessions are recommended per week with an interval of at least two days between two sessions. Depending on the stubbornness of the psoriasis, it can take from 4 to 10 treatment sessions to see the results. How long the improvement lasts is something that cannot be said with certainty.

Side effects

This treatment can cause side effects such as redness of the skin and skin blisters.

2. Goeckerman Therapy

Goeckerman treatment combines the use of coal tar treatment with UVB light rays. This combination is more effective than when either of these therapies is used alone because coal tar makes the skin more receptive to UVB light rays.

Over the years this treatment has undergone modification and treatment sessions are now given as outpatient procedures instead of indoor ones (requiring admissions).

3. Pulsed Dye Laser

A pulsed Dye Laser is used to treat chronic and localized psoriasis skin patches. It involves the use of a dye with a special wavelength of UVB light, which is different than the one used in excimer laser and other UVB treatments. This treatment acts by destroying the tiny blood vessels that contribute to the formation of psoriasis lesions.


In this type of phototherapy, 5 to 30-minute sessions are given every three weeks. In cases responding to this treatment, it takes four to six sessions to clear the psoriasis.

Side effects include bruising and subsequent scarring.

Effectiveness of phototherapy

It is estimated that phototherapy or light therapy significantly controls psoriasis symptoms in 50 to 90 percent of people.

Some types of light therapies are quite effective but carry risks. For example, PUVA combined with oral psoralen tablets is more effective than narrowband UVB phototherapy in controlling the symptoms but the associated risk of skin cancer may be more. The dermatologist, therefore, has to carefully weigh the pros and cons before deciding on the course of the therapy.

PUVA therapy combined with a bath with psoralen added relieves psoriasis symptoms more effectively than UVB phototherapy alone.

Light therapy combined with bathing in water to which bath salts are added appears to be more effective than using UV light therapy alone. However, it is less effective than PUVA therapy combined with psoralen added to a bath.