Phototherapy (light therapy)

About light therapy

Natural sunlight can help to improve your symptoms of, or prevent, many inflammatory skin conditions, such as psoriasis and eczema. It’s a part of sunlight that you can't see, called ultraviolet light, which has this beneficial effect. In light therapy, machines are used to produce ultraviolet light, which is shone on your whole body or the area of your skin that needs treatment.

Types of light therapy

Ultraviolet light is made up of different wavelengths, including the two forms that are used in light therapy – ultraviolet A (UVA) and ultraviolet B (UVB).

UVA on its own causes gradual skin pigmentation (tanning), but has little effect on skin inflammation. For treatment of skin disease, UVA is given together with a chemical, which sensitises your skin to the light (termed ‘psoralen’). Psoralen given with UVA is known as PUVA. PUVA is a more intensive treatment, so you will usually only have it if treatment with UVB hasn't worked for you.

UVB therapy includes broad-spectrum UVB (which uses the full spectrum of UVB radiation) and narrow-band UVB (which focuses on a small part of the light spectrum). Narrow-band UVB is becoming more common because the reduced spectrum avoids some of the more harmful wavelengths. It’s more intensive than broad-spectrum UVB, so treatment times are often shorter.

Children can have UVB treatment but they need to be able to stand or sit still during the treatment and it’s also safe if you’re pregnant. However, PUVA isn’t a suitable treatment for children or if you’re pregnant.

Although light therapy can often completely clear many skin problems, it's not usually a permanent cure.

Where to get light therapy

Your GP will refer you to a dermatologist (a doctor who specialises in identifying and treating skin conditions) to have light therapy in a hospital. High street sunbeds aren’t an effective treatment for skin disorders, as they produce a different type of light.

You will need to attend hospital between two to three times a week for a course of light therapy and most people have between 15 and 30 treatments.

It’s also possible to have some types of light therapy at home. However, home phototherapy isn’t widely used in the UK mainly due to concerns over safety. If home phototherapy is an option, you will usually have your initial treatment at hospital and then begin using a light unit at home. You must follow your dermatologist's instructions and continue to have regular check-ups. Ask your dermatologist for more information.

What are the alternatives of light therapy?

Your dermatologist may only suggest light therapy if other treatments for your condition, such as emollients (moisturisers) and medicated creams, haven't worked for you. Some skin conditions are best treated by light therapy.

Depending on what you’re being treated for, if light therapy doesn't work, or you’re unable to have it for any reason (for example, if it’s not available in your area), your dermatologist may prescribe you a medicine to take instead.

Preparing for light therapy

Your dermatologist will explain how to prepare for your procedure. He or she will discuss with you what will happen before, during and after your procedure, and any pain you might have. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead, which you may be asked to do by signing a consent form.

While you’re receiving a course of light therapy, you will need to limit any additional exposure to natural ultraviolet light in sunlight and make sure you don't put anything on your skin that can enhance the effects of the light. Your doctor may advise you to:

  • cover your skin when out in sunlight and not to use sunbeds
  • not eat too many foods that contain natural psoralen and so make you more sensitive to ultraviolet light – these include celery, carrots, figs, citrus fruits, parsnips and parsley
  • not use perfumed products, creams, ointments and lotions unless told to by hospital staff
  • not cut your hair during the treatment course as it may expose skin that was previously covered by hair

Before a treatment session, it's also important to let the hospital staff know about any new medicines you have started taking (including any herbal medicines), as some medicines can make your skin more sensitive to light.

What happens during light therapy?

If you’re having PUVA treatment, you will usually be asked to take a psoralen tablet two hours before your UVA therapy. Alternatively, you may be able to use a form of psoralen that you can add to bath water, but you will have the bath in hospital. You can also have psoralen as a cream or gel if you’re getting treatment for small areas of your skin. If you have had tablet psoralens, you will be asked to wear UV protective glasses for 24 hours to prevent damage to your eyes as psoralen makes your eyes, as well as your skin, more sensitive to natural sunlight.

Usually a trained phototherapy nurse at a hospital will administer your light therapy. Your dermatologist will work out the best dose for you to start on, based on your skin type and how easily you usually burn in sunlight. A test dose of ultraviolet light may be applied to a small area of your skin to help calculate the correct starting dose of ultraviolet light.

You will be asked to undress in a treatment room, but keep your underpants on. You will also be given goggles to wear to protect your eyes during treatment. You may be asked to apply sunscreen to protect certain parts of your skin, such as your neck, lips and nipples.

The ultraviolet light is produced by fluorescent tubes placed in specially designed cabinets. If you’re having treatment for your palms and soles, you may be able to have treatment using a small unit where you will just need to place your hands or feet in the unit.

In the first few sessions, your treatment may last for less than a minute. The duration may be gradually increased in later sessions to a number of minutes, depending on how you respond to light therapy.

What to expect afterwards

You will usually be able to go home when you feel ready. Your nurse or dermatologist will give you some advice on how to manage any side-effects.

If you have had PUVA, you will be asked to carry on wearing sunglasses for 24 hours from the time you took psoralen to protect your eyes, and to make sure your skin is fully covered if you’re outside or inside near a window.

What are the risks?

As with every procedure, there are some risks associated with light therapy. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your dermatologist to explain how these risks apply to you.


Side-effects are the unwanted but mostly temporary effects you may get after having the procedure.

The possible side-effects of light therapy include:

  • red skin, similar to sunburn – this should fade over the following days after your treatment, and you can use moisturisers to help relieve any discomfort
  • dry and itchy skin – moisturisers may help to relieve this
  • a rash
  • cold sores (if you get them)
  • feeling sick (if you have had PUVA treatment) – your dermatologist may suggest that you try a different type of medicine or use a PUVA bath at your next session if you feel sick with psoralen tablets


Complications are when problems occur during or after your treatment.

As with natural sunlight, repeated sessions of UVB and PUVA light therapy can increase your risk of skin cancer and premature skin ageing over the long term. The risk is higher the more sessions of light therapy you have. Because of this, your dermatologist will always make sure that you receive the least amount of UVB or PUVA light therapy possible that will provide a beneficial effect. He or she will also keep a record of the amount of light therapy you have had in total, to make sure your dose is within safe exposure limits.

There is also a risk of damage to your eyes with PUVA. However, wearing eye protection will reduce this risk.

Why can't I just use natural sunlight and sunbeds to treat my psoriasis?


Natural sunlight is known to be helpful for many people with psoriasis. However, it can be hard to control how much you get and keep it within a safe amount. Sunbeds are of limited or even no value in treating psoriasis, as they don’t usually produce the most effective wavelength of light.


Ultraviolet light therapy in a hospital is carefully controlled in terms of both the dose that is delivered to your skin and the wavelength of the light used. Both of these factors will be recorded as your treatment is gradually increased. This means you can be given the most effective light treatment in the safest way.

While natural sunlight can be helpful for people with psoriasis, you need to be careful to avoid overexposure to the sun and sunburn. Talk to your doctor about how to get the most from the sun while keeping safe. If you’re already receiving light therapy in hospital, you will be advised to avoid sunlight during a treatment course.

Unfortunately, high street sunbeds aren’t tightly controlled, so the exact spectrum of light emitted or dose of light delivered may not be optimal to balance treating the condition against your risk of skin cancer. In addition, the amount of UVB light, which is the most effective type of light for treating psoriasis, is frequently reduced in high street units, as it can be associated with burning if not used carefully. This means that the light produced by sunbeds may be of no benefit in treating psoriasis or it may even be harmful. There is very good evidence demonstrating the link between sunbed use and the risk of skin cancer.

Is light therapy for seasonal affective disorder (SAD) the same as that for skin conditions?


No. With SAD, you can buy your own light-emitting device, such as a light box or dawn simulator, to use at home or at work. You don't have to go to hospital for this type of light therapy as it’s a different type of light to that used in the treatment of skin conditions.


The devices that are used for this type of light therapy contain bright light tubes that emit visible (non-ultraviolet) light at least 10 times the intensity of ordinary household light bulbs. To use them, you need to make sure the light is directed towards your eyes.

Light therapy for skin conditions uses only the ultraviolet part of light, as this is the part that is beneficial. You will usually have it in a hospital under the supervision of medical staff. It’s directed at your skin, while your eyes are protected.

Should I carry on using creams and other treatments for psoriasis while I have light therapy?


It can be effective to take other treatments at the same time as having light therapy, but talk to your dermatologist about what is best for you.


It can help to carry on using emollients during your treatment, as it can stop scales from building up on your skin, which can affect how much UV light penetrates your skin. However, ask your dermatologist for advice about any creams you’re using as some may protect your skin from the light and reduce the effect of the treatment.

If you’re taking tablets for psoriasis, it’s important to let your dermatologist or phototherapy nurse know, as some tablets can increase your skin’s sensitivity to sunlight.

It can sometimes help to clear your psoriasis faster if you take other treatments, such as medicated creams, at the same time as having UVB or PUVA light therapy. Using creams and ointments at the same time as light therapy may also help if your psoriasis isn't responding to either treatment on its own. Your dermatologist will tell you if he or she thinks this is an appropriate treatment for you.