Ultraviolet Light Therapy

There are two different types of ultraviolet ‘UV’ light therapy that are used to treat psoriasis: Narrowband UVB and PUVA.

Many people with psoriasis notice an improvement in their skin after they have been in the sunshine. The use of the sun’s rays has been used to treat psoriasis for over a century, however, of the many different ultraviolet rays emitted by the sun, only UVA and UVB are helpful to people with psoriasis. Ultraviolet light reduces inflammation in the skin, which is why it can be effective for psoriasis and other inflammatory skin conditions.

What is Narrowband UVB treatment?

Narrowband UVB is used to treat guttate and plaque psoriasis that is particularly widespread or has not responded to topical (applied to the skin) treatments. Narrowband UVB treatment may sometimes also be referred to as ‘TL-01’ – this is the name of the most commonly-used narrowband UVB lamp.

UVB treatment is given in a phototherapy unit – usually in a hospital Dermatology department or clinic - by a team of health professionals. A Dermatologist calculates precisely how much UVB light each person’s skin should be subjected to, and will increase the exposure over the course of the sessions.

Treatment is usually given two or three times a week, for up to ten weeks. The individual stands in the UVB cabinet for a period of a few seconds to several minutes at a time. Depending on which areas of the body are being treated, they may be advised to cover up certain areas, and leave other areas exposed. You should always ask your Dermatologist or the member of staff administering the UVB treatment if you have any questions about this.

What is PUVA treatment?

PUVA is a combination of UVA light and a chemical called psoralen (P). UVA is not beneficial in treating psoriasis on its own; instead it must be combined with psoralen (a chemical derived from plants) which makes the skin more sensitive to the UVA light. Psoralen can be taken as a tablet, applied to the areas of the skin being treated as a gel or cream, or added to bath water to soak the whole body. It will depend on what areas of the body are being treated as to which method is used.

PUVA is used to treat moderate to severe plaque psoriasis that has not responded to topical treatments, or UVB therapy. PUVA can be more successful on thicker plaques of psoriasis than UVB, as the UVA is absorbed deeper in the skin. For the same reason, hand and foot psoriasis is often treated with PUVA therapy.

Like UVB, PUVA is given in a phototherapy unit and administered by a team of health professionals. A Dermatologist calculates precisely how much UVB light each person’s skin should be subjected to, and will increase the exposure as appropriate over the course of the sessions. Treatment is usually given twice a week, for a period of five to eight weeks. The individual stands in the PUVA cabinet (or puts their hands or feet into a unit designed specifically for treating psoriasis in these areas) for a period of a few seconds to several minutes at a time.

Psoralen makes both the skin and the eyes more sensitive to UVA, and so protective goggles are provided during treatment, and areas that are not being treated must be covered up. UVA-protective glasses should also be worn for up to 24 hours after treatment. You should ask your Dermatologist or Dermatology Nurse for advice on what sort of glasses to purchase, and where they can be purchased from.

When is UV Therapy used?

The National Institute for Health and Care Excellence (NICE) recommends that UVB therapy be offered to people with plaque or guttate psoriasis that cannot be controlled with topical (applied to skin) treatments alone. They are likely to have tried a number of different topical treatments before being offered UVB therapy (see the Treatments from a GP leaflet for more information on topical treatment). It recommends that PUVA treatment be considered to treat palmoplantar pustulosis (pustular psoriasis on the palms and soles).

If it is found that some areas of psoriasis are slow to respond, do not show a satisfactory response, or are in some hard-to-treat areas (such as the scalp and sensitive areas), a topical treatment might be prescribed alongside UV therapy. It is important to remember that the effects of UV therapy are temporary – in most cases the psoriasis will come back at some point. If psoriasis is returning very quickly after a course of UV therapy, it may be time to move on to another type of treatment.

What are the risks/side effects of UV therapy?

  • Exposure to UV light (A or B) can cause skin damage, premature ageing and increases the risk of skin cancer. However, it is important to note that this is true of natural sunlight as well as artificial UV light. For these reasons, the British Photodermatology Group have issued guidelines as to the total number of UV treatments an individual can have in a lifetime.
  • Some redness of the skin and tanning is likely, but you should let the staff in the department know if you experience any burning sensations (these usually occur 12-24 hours after treatment).
  • If you are using other treatments, including topical (applied to skin) treatments, you should check with your doctor or pharmacist that it is appropriate to keep using it during your UV treatment. This is because some other treatments can make the skin more sensitive to UV light, which may increase the likelihood of side effects if used at the same time.
  • UV treatment can make the skin dry and itchy – apply plenty of moisturiser after treatment in order to overcome this. However, if the itching continues or gets worse, do tell the phototherapy staff or your Dermatologist.
  • Oral Psoralen (tablet) used in PUVA can make some people feel sick. Do tell your Dermatologist if this happens for you, as they may be able to change the type of Psoralen, or prescribe another medication to help you stop feeling sick.

Sunbeds, sunlamps and natural sunshine

Using a sunbed at a gym, salon or spa is not the same as having UV therapy in a hospital setting. Firstly, hospital-based UV treatment uses only the specific part of the spectrum that is useful to treat skin conditions. This is not the case on a sunbed, where a much broader spectrum is used. Many sunbeds use mostly, or entirely, UVA light, which is ineffective for treating psoriasis without the added psoralen. Therefore, using sunbeds means taking on the risks of UV exposure, without much of the benefit to psoriasis.

UV treatment in hospital is very carefully controlled – a Dermatologist will administer the right amount of exposure for each individual, and monitor the results. If a person uses sunbeds or an at-home lamp in addition to this, it makes it difficult to ensure they are receiving the correct dose for them.

It is also important to follow sun safety advice, even if your psoriasis improves in the sunshine, in order to prevent potential side effects such as skin cancer and premature ageing. Sunburn can actually aggravate psoriasis or trigger a flare, so do use a suncream with a high SPF (NHS sun safety advice recommends SPF 15 or above) and re-apply it regularly. Aim to cover up with a hat, t-shirt and sunglasses, and avoid being out in the intense sunlight in the middle of the day.


The information on this page is also available in our UV treatment information sheet

October 2018 (Review Date: October 2021)