Light therapy (phototherapy) for skin conditions

Expert reviewer, Dr Veronique Bataille, Consultant Dermatologist
Next review due May 2025

Light therapy – also known as phototherapy – uses controlled artificial ultraviolet (UV) light to help reduce the symptoms of some types of skin conditions. These include eczema, psoriasis and vitiligo (when patches of your skin lose their colour).

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About light therapy

Ultraviolet (UV) light is an invisible part of natural sunlight. Light therapy machines produce carefully measured levels of ultraviolet light. A health professional trained in carrying out light therapy will shine this on either your whole body, or an area of skin that needs treatment. This is usually a registered nurse or physiotherapist. You’ll usually have light therapy in a hospital or clinic, and have it two to five times a week, for 12 to 16 weeks. This will depend on the type of light therapy you have.

Light therapy can help with skin conditions where your skin is inflamed, like psoriasis, vitiligo or eczema. The ultraviolet light reduces your body’s immune response, and reduces the inflammation in your skin. Light therapy may help ease itchy skin from eczema too. It’s not usually a permanent cure for skin conditions, but aims to reduce symptoms.

If you have an inflammatory skin condition and standard treatments such as moisturisers and creams don’t help, your GP may refer you to a dermatologist. This is a doctor who specialises in identifying and treating skin conditions, and they’ll assess you to see if light therapy is suitable for you.

High-street sunbeds aren’t the same as light therapy because the type of UV and the intensity are very different. Do not use these for skin conditions.

High-street sunbeds aren’t tightly regulated so you won’t know the amount of UV you’re exposed to. This means you can’t balance treating your condition against the risk of skin cancer from a sunbed. Many sunbeds also use mostly, or entirely, UVA light. The light produced by these sunbeds may be of no benefit in treating your skin condition and may even be harmful.

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 therapy can be used alone, or together with a chemical called psoralen, which causes your skin to become more sensitive to the light. Psoralen with UVA is known as PUVA. You can take psoralen as a tablet, soak parts (or all) of your body in a psoralen solution, or apply a psoralen gel on affected areas.
  • UVB therapy is usually narrow-band UVB (that uses just a small part of the UVB spectrum) rather than broad-band UVB (that uses the full UVB spectrum). This is because it avoids some of the more harmful wavelengths.

PUVA is a more intense treatment, so your doctor might only recommend it if treatment with UVB hasn't worked for you. But it can be a better option for certain conditions, like pustular psoriasis and moderate-to-severe eczema on your hands and feet, for example.

Suitability for light therapy

Your dermatologist will meet you to discuss the benefits, risks and alternatives to the procedure, and assess whether light therapy is suitable for you.

They may examine you and ask you questions about your medical history, including the following.

  • Whether you’re taking any other medicines, including anything you put on your skin.
  • If you have any allergies to medicines.
  • Whether you have any history of eye conditions, especially cataracts.
  • If you have any conditions that affect other organs in your body, such as your kidney or liver.
  • If you have allergy to the sun, or if you have a rare health condition called lupus.
  • If you’re pregnant or trying to get pregnant. PUVA is not recommended during pregnancy; but you should be able to have UVB.
  • Your risk of developing skin cancer. Light therapy may not be recommended if you’ve had skin cancer or you have a family history of the disease.

You’ll need to be able to attend regular sessions of phototherapy (usually two to three sessions a week) and be able to stand up unaided for at least 10 minutes.

If your dermatologist thinks that light therapy is suitable for you, they’ll arrange for you to have an assessment with a phototherapist. They’ll run through all the practical details about light therapy treatment with you. Be sure to ask any questions you have. If you’re happy to go ahead with the procedure, you’ll be asked to sign a consent form – so it’s important to make sure you feel you have all the information you need.

The phototherapist 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 the sun. They’ll apply one or more test doses of ultraviolet light to small areas of your skin to check your skin’s sensitivity. How these patches of skin react will help calculate the right dose for you to start on.

Preparing for light therapy

Your phototherapist may ask you to do some of the following during light therapy treatment.

  • Limit your exposure to any additional ultraviolet light – cover your skin when out in the sun, and don’t use sunbeds.
  • Don’t eat a lot of foods that contain natural psoralen, as these can make you more sensitive to ultraviolet light. Psoralen is found in celery, carrots, figs, citrus fruits, parsnips and parsley, for example.
  • Don’t use perfumed products, creams, ointments and lotions on treatment days because they may contain things that make your skin more sensitive to light. But you can use them after each treatment. You can use a water-based moisturiser before your treatment, and this can help your skin to absorb the ultraviolet light. Check your product with your phototherapist first.
  • Let your phototherapist know if you’ve cut your hair during your course of treatment, as you may expose skin that was previously covered by hair.
  • Let them know if you take any medicines for other conditions (including any herbal medicines), and update your phototherapist if you take anything new between sessions. Some medicines can make your skin more sensitive to light, and some can interact with psoralen that you take for psoralen ultraviolet A (PUVA) light therapy.
  • Psoralen can increase your response to caffeine and give you headaches or make you jittery. You may need to cut down on drinks that contain caffeine on the days you have light therapy treatment.
  • Don’t drink alcohol before a treatment session.

Light therapy procedure

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, your hospital or clinic will give you some instructions on how to take the psoralen before your session. You may need to:

  • take a psoralen tablet with a light meal, a couple of hours before your therapy session
  • have a psoralen bath at the hospital or clinic before your therapy (or just soak your hands and feet if those are the only parts that are being treated)
  • apply psoralen cream, lotion or gel if you’re getting treatment for small areas of your skin

If you’ve had a psoralen tablet, your hospital or clinic will ask you to wear ultraviolet protective glasses from the time you take your tablet, until 24 hours after your light therapy. Wear them in daylight and indoors where you’re exposed to light. This is to prevent damage to your eyes, because psoralen makes your eyes more sensitive to natural sunlight.

At the start of your session, you’ll need to remove any clothing from the area that’s to be treated. If your whole body is being treated, you’ll need to take all your clothes off but a genital shield will be used to cover your penis if you have one. You’ll also need to wear goggles to protect your eyes or a clear visor to cover your face if it’s not being treated. Your hospital or clinic may tell you to put sunscreen on to protect certain parts of healthy skin, such as your lips.

If you’re having your whole body treated, you’ll have the light therapy in a walk-in ‘cabin’ fitted with fluorescent tubes that give out ultraviolet light. The cabin will be ventilated to control the temperature. There are sensors in the cabin that make sure you get the correct level of exposure. You can easily open the door to stop treatment if you feel uncomfortable.

If you’re having treatment for your palms and/or soles of your feet 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 gradually increase in later sessions, depending on how you respond to light therapy.

Aftercare for light therapy

You’ll usually be able to leave the hospital or clinic as soon as your treatments finished. Your phototherapist will give you some advice on how to manage any side-effects.

Protect yourself from the sun while you’re having a course of light therapy. For example, cover your skin with clothing and a hat, and use a high-factor sunscreen. Don’t use sunbeds or sunbathe while you’re having treatment.

You’ll need to take extra precautions if you’ve had psoralen ultraviolet A (PUVA) because it makes your skin especially sensitive. You’ll need to stay out of the sun for 12 to 24 hours after your treatment. Keep your ultraviolet protective glasses on during this time to prevent a future risk of cataracts. This includes wearing them outside, and when you’re near a window or indoor lighting that can emit UVA, as some energy-saving fluorescent lamps do.

Side-effects of light therapy

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

Short-term side-effects

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

  • Red skin, similar to mild sunburn.
  • Dry and itchy skin.
  • A spotty, itchy rash.
  • Infected hair follicles (folliculitis).
  • Cold sores (if you get them). If you put high-factor sunscreen on your lips during your treatment and take your usual medicines to prevent them, it may reduce the risk.
  • Blisters on your skin.
  • Feeling sick. This may happen if you take a psoralen tablet before PUVA therapy. It may help to take the tablets with a little food, or you might be able to have a different type of psoralen tablet. Another option is to apply psoralen to your skin or as a bath soak instead.


Long-term side-effects

As with natural sunlight, light therapy can increase your risk of skin cancer and premature skin ageing over the long term. There’s more of a clear link of this risk with PUVA therapy. It’s unclear what the exact risk of skin cancer is with ultraviolet B (UVB) light therapy, but it’s thought to be less than with PUVA.

Your dermatologist and phototherapist will do everything they can to ensure your risk of skin cancer from phototherapy is as low as possible. For example, they will:

  • provide shields for more sensitive parts of your body like your face and genitals
  • use the lowest dose of UVB or PUVA possible to provide a beneficial effect
  • keep a record of the amount of light therapy you’ve had in total to make sure your exposure remains within safe limits over a course of treatment and during your lifetime
  • if you’ve had a lot of light therapy, monitor you regularly for signs of skin cancer
  • give you information about how to protect your skin and reduce your exposure to UV light following treatment

There's also a risk of damage to your eyes with PUVA, especially if you’ve had cataracts. If you wear eye protection, it will reduce this risk.

Your clinic will monitor the cumulative (increasing) dose you’ll receive over months or years if you have repeated courses over time. This will make sure you don’t exceed the maximum dose over your lifetime.

Frequently asked questions

  • Skin conditions that can be treated with phototherapy include eczema, psoriasis and vitiligo (when patches of your skin lose their colour). Phototherapy reduces the inflammation in your skin. While it’s not usually a cure, it often reduces symptoms of these skin conditions.

    See our section: About light therapy above for more information.

  • There are phototherapy units that you can use at home. These are usually used in remote places where people don’t have easy access to a hospital or clinic to have phototherapy. But it’s best to have treatment at a hospital or clinic because it’s very important to accurately measure the dose of UV light. This will ensure your treatment is safe and you lower the chance of any side-effects. It’s difficult to monitor the doses of home phototherapy over time, and the types of sunbeds available for home use are very different from those used in clinics or hospitals.

    See our section: Side-effects of light therapy above for more information.

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Related information

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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, May 2022
    Expert reviewer, Dr Veronique Bataille, Consultant Dermatologist
    Next review due May 2025