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Light therapy (phototherapy) for skin conditions


Expert reviewer, Dr Anton Alexandroff, Consultant Dermatologist
Next review due, December 2022

Light therapy – also known as phototherapy – uses controlled artificial ultraviolet light to help reduce symptoms of common skin conditions. These can include 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. Light therapy machines produce carefully measured levels of ultraviolet light, which is shone onto your whole body or the area of your skin that needs treatment. You’ll usually have light therapy in a hospital or special clinic. You’ll need to have it two or three times a week, for a couple of months.

Light therapy can help with skin conditions where your skin is inflamed, like psoriasis, eczema or vitiligo. The ultraviolet light dampens down your body’s immune response, and reduces the inflammation in your skin. 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 aren’t controlling your symptoms, your GP may refer you to a dermatologist to assess your suitability for light therapy. A dermatologist is a doctor who specialises in identifying and treating skin conditions.

High-street sunbeds don’t provide light therapy and you should avoid using them for skin conditions. For more information, see our FAQ: Does a tanning bed help with skin conditions?

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 is usually used together with a chemical called psoralen, which causes your skin to become more sensitive to the light. Psoralen with UVA is known as PUVA.
  • UVB therapy can be broad-band UVB (using the full UVB spectrum) or narrow-band UVB (using just a small part of the UVB spectrum). Doctors usually recommend narrow-band UVB because it avoids some of the more harmful wavelengths.

PUVA is a more intensive treatment, so you might only be offered 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.

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 apply to your skin.
  • If you have any allergies to medicines.
  • Whether you have any history of eye conditions, especially cataracts.
  • If you have any problems affecting your kidney or liver. Treatment with Psoralen with UVA (PUVA) may be unsuitable for you if so; but you may still be able to have treatment with ultraviolet B (UVB).
  • 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 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. A phototherapist is a health professional – usually a registered nurse or physiotherapist – trained in carrying out light therapy. They will 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 properly informed.

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

Preparing for light therapy

Your phototherapist is likely to ask you to follow certain rules during light therapy treatment. These may include the following.

  • Limit your exposure to any additional ultraviolet light – cover your skin when out in sunlight, 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. These include celery, carrots, figs, citrus fruits, parsnips and parsley. Avoid these foods for at least two hours before a session.
  • Don’t use perfumed products, creams, ointments and lotions on treatment days, unless told to by your phototherapist.
  • 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, let your phototherapist 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.

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

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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 be told how to take the psoralen before your session. This may be:

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

If you’ve had a psoralen tablet, you’ll be asked to wear ultraviolet protective glasses from the time you take your tablet, until at least 12 hours after your light therapy. 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 be asked to remove any clothing from the area to be treated. If your whole body is being treated, you’ll need to undress fully – but men will need to 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.

If you’re having your whole body treated, you’ll have the light therapy in a specially designed walk-in ‘cabin’ fitted with fluorescent tubes that give out ultraviolet light. Fans provide ventilation and control the temperature. Sensors in the cabin make sure you get the prescribed level of exposure. You can easily open the door to stop treatment if you feel at all uncomfortable.

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.

What to expect afterwards

You’ll usually be able to leave the hospital or clinic as soon as your treatment’s finished. Your phototherapist 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) while you’re having a course of light therapy.

You’ll need to take extra precautions if you’ve had Psoralen ultraviolet A (PUVA), which makes your skin especially sensitive. You’ll need to avoid any sun exposure for 12 to 24 hours after your treatment, and carry on wearing ultraviolet protective glasses during this time. 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.

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 sunburn. With psoralen with UVA (PUVA), this might not happen until two to three days after your treatment.
  • Dry and itchy skin.
  • A rash.
  • Infected hair follicles (folliculitis), which can be soothed with moisturisers.
  • Cold sores (if you get them). Covering your lips with high-factor sunscreen during treatment and taking your usual medicines to prevent them can reduce the risk.
  • Blisters, especially if you’re fair skinned.
  • 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, or you may prefer 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 take several measures to ensure your risk of skin cancer remains as low as possible. These include:

  • providing shields for more sensitive parts of your body like your face and genitals
  • making sure that you receive the lowest dose of UVB or PUVA possible to provide a beneficial effect
  • keeping 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, monitoring you regularly for signs of skin cancer
  • giving 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 or are missing a lens from your eye. However, wearing eye protection will reduce this risk.

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 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.

  • No. Light therapy for seasonal affective disorder (SAD) is a different type from the one used for skin conditions. The devices that are used for this type of light therapy emit visible (non-ultraviolet) light at a much higher intensity than that of ordinary household lights. 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 used for skin conditions.

    Light therapy for SAD doesn’t need to be done in a hospital or clinic. You can buy your own light-emitting device, such as a light box or dawn simulator, to use at home or at work. You’ll usually need to use it for 30 minutes or more a day, in order to get a beneficial effect.


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Related information

    • Phototherapy. British Association of Dermatologists. www.bad.org.uk, updated July 2018
    • Chen X, Yang M, Cheng Y, et al. Narrow‐band ultraviolet B phototherapy versus broad‐band ultraviolet B or psoralen‐ultraviolet A photochemotherapy for psoriasis. Cochrane Database of Systematic Reviews 2013, Issue 10. Art. No.: CD009481. DOI: 10.1002/14651858.CD009481.pub2
    • Mosely H, Allan D, Amatiello H, et al. Guidelines on the measurement of ultraviolet radiation levels in ultraviolet phototherapy: report issued by the British Association of Dermatologists and British Photodermatology Group 2015. Br J Dermatol 2015; 173(2):333–50. doi: 10.1111/bjd.13937
    • Psoriasis: assessment and management. National Institute for Health and Care Excellence (NICE), updated September 2017. www.nice.org.uk
    • Psoriasis. NICE Clinical Knowledge Summaries. cks.nice.org.uk, last revised March 2018
    • Eczema. BMJ Best Practice. bestpractice.bmj.com, last reviewed October 2019
    • UV therapy. Psoriasis Association, October 2018. www.psoriasis-association.org.uk
    • Ling TC, Clayton TH, Crawley J, et al. British Association of Dermatologists and British Photodermatology Group guidelines for the safe and effective use of psoralen–ultraviolet A therapy 2015. Br J Dermatol 2016; 174(1):24–55. doi: 10.1111/bjd.14317
    • Phototherapy service guidance. British Association of Dermatologists, issued October 2016. www.bad.org.uk
    • Service guidance and standards. Phototherapy. British Association of Dermatologists. www.bad.org.uk, accessed 26 November 2019
    • Consent: patients and doctors making decisions together. General Medical Council, June 2008. www.gmc-uk.org
    • Personal communication, Dr Anton Alexandroff, Consultant Dermatologist, 28 November 2019
    • PUVA. PatientPlus. patient.info, last reviewed 20 June 2014
    • Nussbaumer B, Kaminski‐Hartenthaler A, Forneris CA, et al. Light therapy for preventing seasonal affective disorder. Cochrane Database of Systematic Reviews 2015, Issue 11. Art. No.: CD011269. DOI: 10.1002/14651858.CD011269.pub2
    • Pail G, Huf W, Pjrek E, et al. Bright-light therapy in the treatment of mood disorders. Neuropsychobiology 2011; 64:152–62. doi: 10.1159/000328950
  • Reviewed by Pippa Coulter, Freelance Health Editor, December 2019
    Expert reviewer Dr Anton Alexandroff, Consultant Dermatologist
    Next review due December 2022



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