Light therapy (phototherapy) for skin conditions

Expert reviewer, Dr Anton Alexandroff, Consultant Dermatologist
Next review due August 2020

Light therapy, or phototherapy, uses controlled artificial ultraviolet light to help reduce symptoms and slow the progress of common skin conditions such as eczema, psoriasis and vitiligo (when patches of your skin lose their colour).

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What is light therapy?

Ultraviolet light is an invisible part of natural sunlight. It can help to improve common skin conditions. Light therapy machines produce carefully measured levels of ultraviolet light, much stronger than levels in sunlight. This is shone onto your whole body or just the area of your skin that needs treatment.

Your GP will refer you to a dermatologist to have light therapy in a hospital or a special clinic. A dermatologist is a doctor who specialises in identifying and treating skin conditions. Normally, a specially trained phototherapist will carry out the procedure.

Light therapy involves short but regular sessions – two or three times a week – for a couple of months at a hospital or dermatology clinic.

You’ll need to take extra care to protect your skin before and after sessions.

How does light therapy work?

In eczema, psoriasis and vitiligo, the ultraviolet light stops your skin getting so inflamed. Light therapy treatment also limits the overproduction of skin cells that build up to form the plaques of hard skin common in psoriasis.

Your doctor may suggest light therapy if you have severe flare-ups that your usual treatment – like moisturisers and anti-inflammatory medical creams – doesn’t help enough. It can completely clear many skin problems, but it's not usually a permanent cure and you may need more treatments.

Light therapy can also be used for other skin conditions such as some types of lymphoma, pityriasis (a temporary harmless rash causing red, raised scaly patches on the body), and lichen planus (a non-contagious itchy rash).

What are the different types of light therapy?

Ultraviolet light is made up of different wavelengths. Two forms are used during light therapy – ultraviolet A (UVA) and ultraviolet B (UVB). UVA in natural sunlight is what causes your skin to tan, and may lead to long-term damage like wrinkles. UVB is the main cause of sunburn. Although light therapy uses these rays, they are used in a controlled way so that they are as safe as possible. Your dermatologist will talk to you about the risks and discuss any concerns and questions you may have.

Broad-band UVB and narrow-band UVB

UVB therapy can be broad-band UVB or narrow-band UVB. Broad-band UVB uses the full spectrum of UVB radiation while narrow-band UVB uses a small part of the UVB radiation.

Doctors recommend narrow-band UVB because it avoids some of the more harmful wavelengths. This means you’re less likely to have side-effects. It’s more intensive than broad-spectrum UVB, so treatment times are often shorter.

Psoralen ultraviolet A (PUVA)

To treat skin conditions, UVA is usually used together with a chemical called psoralen, which is found in plants. This causes your skin to become more sensitive to the light. Psoralen with UVA is known as PUVA.

PUVA is a more intensive treatment, so you may only have it if treatment with UVB hasn't worked for you. But it can be a better option for specific conditions like pustular psoriasis and when psoriasis plaques are particularly thick and white. It works well for moderate to severe eczema, especially on your hands and feet.

Can anyone have light therapy?

Your dermatologist may suggest light therapy only if other treatments for your condition, such as emollients (moisturisers) and medicated creams, haven't worked.

Some skin conditions are best treated by light therapy. It can be used in combination with other treatments, including some medicines.

Ultraviolet B (UVB) treatment is generally safe for children and pregnant or breastfeeding women. Psoralen with UVA (PUVA) isn’t suitable for children and isn’t recommended if you’re pregnant, or trying to get pregnant. PUVA can also be unsuitable if you have severe liver or kidney problems.

You need to be able to attend regular sessions of phototherapy for it to be effective. And because of the equipment used, you should be able to stand up unaided for at least 10 minutes. Light therapy may not be recommended if you’ve had skin cancer or are at particular risk of developing it, including your family history.

You may not be able to have light therapy while you’re taking medicines that affect your immune system or sensitivity to sunlight.

There’s also a limit to how many light therapy treatments you can safely have overall but your dermatologist will explain this to you.

If light therapy doesn't work, or you’re unable to have it for any reason, your dermatologist may prescribe you a medicine instead.

Where will I go to have light therapy?

You’ll usually have treatment as an outpatient in the hospital’s phototherapy unit, which may be in the dermatology or physiotherapy department. Some areas – particularly in Scotland – offer narrow-band ultraviolet B (UVB) light therapy under supervision in a person’s home if they cannot get to hospital for treatment.

It depends on your condition, but you’ll usually need to attend hospital at least two to three times a week for a course of light therapy. Exposure to the ultraviolet light will gradually increase to allow your skin to get used to it and begin to improve. People respond differently so it’s hard to predict how long this will take. Most people have between 20 and 30 treatments over about three months.

High street sunbeds don’t provide light therapy and you should avoid using them for skin conditions. Sunbeds normally emit ultraviolet A (UVA) light, which on its own is less effective than UVB at reducing the symptoms and progression of skin conditions. For more information, see our FAQ: Does a tanning bed help with skin conditions?

Checks before having light therapy

Your dermatologist will discuss your care and the procedure with you. This will be designed to meet your individual needs so it may be different from what’s described here.

Before you start a course of light therapy treatment, particularly psoralen with UVA (PUVA), your dermatologist will want to assess possible risks. They may examine you and ask about:

  • other medicines you’re taking, including anything you apply to your skin
  • any allergies to medicines
  • how sensitive you are to light
  • any history of eye conditions, especially cataracts
  • kidney and liver problems
  • your risk of developing skin cancer

Your dermatologist will work out the best dose for you to start on. This is mainly based on your skin type and how easily you burn in sunlight. The level of exposure may vary if you’ve got other medical conditions or are taking medicines that make your skin more sensitive to light. These can include antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen.

To check your sensitivity, one or more test doses of ultraviolet light may be applied to small areas of your skin that aren’t normally exposed to sunlight. Sensitivity to light varies between different parts of your body – your trunk (the central part of your body not including your head, arms or legs) is especially sensitive, so skin there will probably be tested even if your arms, legs or head are being treated. How these patches of skin react will help calculate the right amount of ultraviolet light for your first session, and how long this should last.

Your dermatologist will also have a chat with you about what happens before, during and after light therapy treatment. This is a good opportunity to make sure you understand what will happen. It may help to have a think about what questions you’d like answered. These might include information about the risks, benefits and any alternatives. Once you’re happy, you may be asked to give your consent for treatment to go ahead by signing a consent form.

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Preparing for light therapy

Before and during a course of light therapy, you will need to limit any additional exposure to natural ultraviolet light in sunlight.

Your doctor may give you the following advice.

  • Cover your skin when out in sunlight and don’t use sunbeds.
  • Don’t eat a lot of foods that contain natural psoralen, which will make you more sensitive to ultraviolet light. These include celery, carrots, figs, citrus fruits, parsnips and parsley. You should avoid these for at least two hours before a session.
  • Don’t use perfumed products, creams, ointments and lotions, unless told to by hospital or clinic staff. This may include coal tar or disinfectant soap you use for your condition and some deodorants. Your dermatologist or phototherapist may suggest suitable moisturisers you can use.
  • Don’t cut your hair during your course of treatment as you may expose skin that was previously covered by hair.

Before a treatment session, it's also important to let the hospital or clinic staff know about any new medicines you’ve started taking (including any herbal medicines). This is because some medicines can make your skin more sensitive to light. For example, St John’s Wort is known to increase sensitivity to light.

Psoralen ultraviolet A (PUVA) light therapy can affect your liver and interact with medicines for other conditions, such as warfarin (for blood clotting) and antipsychotics. These may need to be monitored during your course of treatment. The psoralen you take for PUVA can increase your response to caffeine and give you headaches or make you jittery. So your doctor may advise cutting down on drinks containing caffeine on the days you have light therapy treatment.

PUVA may also make some medicines less effective, including calcium channel blockers, statins and oral contraceptives. If you’re taking these, and you and your doctor decide that you should have PUVA, your doctor will give you the lowest possible dose of PUVA to limit the risk while still improving your skin condition. The checks you have before deciding to have light therapy will cover this, and is something for you and your doctor to discuss.

What happens during a light therapy session?

There are slight differences in the procedure depending on the type of light therapy you’re having.

If you’re having psoralen ultraviolet A (PUVA) treatment, you’ll usually be asked to take a psoralen tablet or capsule an hour or two before your therapy session. It’s best to take this with a light meal.

Alternatively, you may be able to use a form of psoralen that you can add to bath water. But you’ll need to have the bath in hospital or the clinic 10 to 15 minutes before your therapy. You can just soak your hands and feet if those are the only parts of your body getting treated.

You can also have psoralen as a cream, lotion or gel if you’re getting treatment for small areas of your skin. You can paint lotion onto white patches of skin affected by vitiligo.

If you’ve had a psoralen tablet, you’ll be asked to wear ultraviolet protective glasses for 24 hours to prevent damage to your eyes. This is because psoralen makes your eyes, as well as your skin, more sensitive to natural sunlight.

Some people prefer to apply psoralen to their skin rather than taking a tablet because there’s less risk of side-effects. They also won’t need eye protection afterwards.

For any type of light therapy, the phototherapist will ask you to remove any clothing from the area to be treated. If your whole body is being treated, you’ll keep your underpants on or use a genital shield. You’ll also be given goggles to protect your eyes or a clear visor to cover your face if it’s not being treated. You may be advised to apply sunscreen to protect certain parts of healthy skin, such as your lips.

You’ll usually be given light therapy in a specially designed walk-in ‘cabin’ fitted with fluorescent tubes that give out ultraviolet light. The tubes are backed by reflectors to help produce the right amount of light. Fans provide ventilation and control the temperature. Sensors in the cabin make sure you get the prescribed level of exposure. These take into account your size and which part of your body is being treated.

If you’re having treatment for your palms and or soles only, a smaller unit can be used to just treat these areas.

In the first few sessions, your treatment may last for less than a minute. The duration will be gradually increased in later sessions, depending on how you respond to light therapy. Applying psoralen to your skin for PUVA makes it more sensitive to light, and can cut the time required.

Most people quickly get used to standing inside the cabin, but you can easily open the door to stop treatment if you’re feeling claustrophobic.

What to expect afterwards

You will usually be able to go home immediately after your treatment. Your phototherapist or dermatologist will give you some advice on how to manage any side-effects.

You should avoid exposure to the Sun or other forms of ultraviolet light (including sunbeds) after any type of light therapy.

But you need to take extra precautions if you’ve had psoralen ultraviolet A (PUVA), which makes your skin especially sensitive. You’ll be asked to carry on wearing ultraviolet protective glasses for 12 to 24 hours. Children and people at risk of cataracts (or who already have them) should be particularly careful. This includes wearing eye protection outside, and when you’re near a window or indoor lighting that can emit UVA, like some energy-saving fluorescent lamps do.

After PUVA, you’ll also need to protect your skin for 12 to 24 hours. Make sure you cover up when you’re outside.

Side-effects of light therapy

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

The following are possible side-effects of all types of light therapy.

  • Red skin, similar to sunburn. This is more likely if you’re taking medicines that make your skin sensitive to light. The redness should fade over the days following your treatment. You can use moisturisers to help relieve any discomfort. Your dermatologist may adjust the level of your next treatment or postpone it until your skin has settled.
  • Dry and itchy skin, particularly when you first start treatment. Moisturisers may help to relieve this. Your doctor may prescribe antihistamines to stop the itching.
  • A rash.
  • Cold sores (if you get them). Covering your lips with high-factor sunscreen during treatment can reduce the risk. Take your usual medicines to prevent them.
  • Blisters, especially if you’re fair skinned.

Psoralen with UVA (PUVA) treatment can have some particular side-effects.

  • Headaches and dizziness.
  • Changes to the colour of skin and nails (which may also loosen
  • Infected hair follicles, which can be soothed with moisturisers.
  • Feeling sick. This is common if you’ve taken psoralen in tablet form before PUVA therapy. It helps to take the tablets with a little food. Your dermatologist may prescribe antiemetics to stop you being sick or suggest you apply psoralen to your skin as a bath soak instead.

Risks and complications of light therapy

As with every procedure, there are some risks associated with light therapy. Ask your dermatologist to explain how these apply to you. The assessment you had before starting light therapy will have highlighted risks linked to other conditions and medicines you’re taking. Your doctor will also take into account your age and how fair your skin is.

Complications are when problems occur during or after your treatment.

As with natural sunlight, repeated sessions of ultraviolet B (UVB) and of psoralen with UVA (PUVA) light therapy can increase your risk of skin cancer and premature skin ageing over the long term. This is why it’s particularly important to shield more sensitive parts of your body like your face and genitals.

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 UVB or PUVA treatment possible to provide a beneficial effect.

They will also keep a record of the amount of light therapy you’ve had in total. This is to make sure your dose is within safe exposure limits over a course of treatment and during your lifetime.

Your doctor may want to monitor you regularly for signs of skin cancer if you’ve had a lot of light therapy. They may also want to check your liver function.

There's also a risk of damage to your eyes with PUVA, especially if you’ve had cataracts or are missing a lens from your eye. However, wearing eye protection will reduce this risk.

You should stop PUVA light therapy if you discover you’re pregnant during a course of treatment. But any treatment you’ve previously had shouldn’t affect subsequent pregnancies.

Frequently asked questions

  • Natural sunlight is known to be helpful for skin conditions such as psoriasis. However, it can be hard to control how much sunlight you get and to keep it within a safe amount. You need to be careful to avoid overexposure that can cause sunburn and increase the risk of skin cancer.

    Talk to your doctor about how to get the most from the Sun while keeping safe. If you’re already receiving light therapy, you will be advised to avoid sunlight during a treatment course.

    Ultraviolet light therapy in a hospital or clinic 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.

  • High street sunbeds shouldn’t be used as a solution for a skin condition because they aren’t tightly regulated. This means you may not receive the exact spectrum of light or dose that effectively balances treating your condition against your risk of skin cancer. In addition, the amount of ultraviolet B (UVB) light, which is the most effective type of light for treating psoriasis, for instance, 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 your skin condition or may even be harmful.

    The same is true of home sunbeds. The type of tube used and the ultraviolet light produced can vary so you won’t know exactly how much exposure you’re getting. It’s harder to build up the amount gradually and sunbeds can damage your skin before it goes red, so you don’t realise.

  • No. Light therapy for seasonal affective disorder (SAD) is a different type from the one used for skin conditions. It doesn’t need to be done in a hospital or clinic.

    Light therapy helps because SAD makes you less sensitive to light so you don’t get as much benefit from normal light. You can buy your own light-emitting device, such as a light box or dawn simulator, to use at home or at work. 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. The wavelength of the light is not the same as in ultraviolet B (UVB) or psoralen ultraviolet A (PUVA) therapy.

    People with SAD usually use a light box for up to an hour a day. Some report feeling better very quickly but in most cases it will take a few weeks to affect symptoms like fatigue.

    UVB or PUVA 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 or clinic under the supervision of medical staff. It’s directed at your skin, while your eyes are protected.

  • Your dermatologist may recommend light therapy in combination with other treatments. This may help to improve your skin condition if your symptoms aren’t clearing with topical (applied to the skin) treatment alone.

    It can help to carry on using emollients during your treatment, as this can affect how much ultraviolet 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 your condition, it’s important to let your dermatologist or phototherapy nurse know, as some tablets can increase your skin’s sensitivity to sunlight.

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  • Reviewed by Natalie Heaton, Specialist Health Editor, Bupa Health Content Team, August 2017
    Expert reviewer, Dr Anton Alexandroff, Consultant Dermatologist
    Next review due August 2020

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