What is phototherapy?

Phototherapy (light therapy) refers to the use of ultraviolet (UV) light to treat moderate to severe eczema in adults and children. To be considered for a course of phototherapy, you or your child will need to have tried topical therapies and found that they do not control your eczema. You or your child will need to be referred to a dermatologist, who will assess your suitability. If phototherapy is recommended, your treatment sessions will be supervised by a nurse or physiotherapist trained in phototherapy.

There are three types of phototherapy used in the treatment of eczema – broadband UVB, narrowband UVB, and UVA. For more information about them, please see our Phototherapy factsheet.

What is ultraviolet light?

In nature UV radiation is part of the electromagnetic (light) spectrum that reaches Earth from the sun. UV wavelengths are classified as UVA, UVB or UVC. UVC has the shortest rays and is mostly absorbed by the ozone layer, so does not reach Earth. Both UVA and UVB penetrate the atmosphere (90% UVA and 10% UVB). UV light is important for health (it helps the body to produce Vitamin D) but it is also responsible for tanning and burning the skin.

How does phototherapy work?

Natural sunlight can help reduce symptoms in eczema for some people by reducing the inflammatory response in the skin. Both UVA and UVB wavelengths are used to treat eczema. There is debate about how phototherapy works, but it is known to reduce inflammation in the skin, thereby having an effect on the immune system.

Phototherapy improves the skin gradually after several weeks of regular treatments (2-3 times per week). There is a reduction in itching, and the eczema slowly clears as treatment continues. Once the skin is clear or almost clear, and the itching has stopped, the frequency of treatment is reduced to ‘wean’ the person off. It is very important that people attend sessions regularly to optimise the chances of treatment success.

When is phototherapy used?

Phototherapy is used for adults and children with moderate to severe eczema that is not responding to conventional treatment with topical steroids and emollients. Phototherapy is not used if the person has a UV-sensitive dermatitis or a photo allergy disorder. People with these types of eczema are best treated in specialist clinics.

PUVA should not be used during pregnancy or if breastfeeding because of the risk of secondary damage caused by the psoralen. However, narrowband and broadband UVB can be used in pregnancy and when breastfeeding.

What are the side effects of phototherapy?

It is normal for people to experience some mild redness within 24 hours of treatment. This usually fades quickly and, if not associated with discomfort, treatment will continue as planned. Despite efforts to prevent burning – i.e. by testing the skin’s sensitivity to light using controlled incremental doses for each treatment, careful skin assessments and asking about any side effects at each visit – occasionally sunburn-type reactions may occur with all types of phototherapy. If this happens, it is important to contact the hospital for appropriate advice. Burning that lasts more than 24 hours is considered to be an adverse effect. In this situation you need to be reviewed by the staff looking after you.

Dryness of the skin is also a common side effect, so it is important to use your emollients after treatment.

Sometimes psoralen tablets can cause nausea – again, adjustments can be made in relation to the type of psoralen tablet to try to prevent this side effect of treatment. Taking the psoralen with food can also help minimise nausea. Try to eat the same amount of food with each tablet to ensure similar absorption and efficacy at each treatment session.

Occasionally eczema may flare at the beginning of a course of phototherapy. This can usually be managed by making adjustments to doses and using topical corticosteroids and emollients to settle the flare.

In people prone to eczema herpeticum (eczema infected with the cold sore virus), phototherapy can sometimes trigger reactivation of the infection. If this happens, you will need treatment with antiviral tablets (e.g. aciclovir). Anyone with a history of cold sores triggered by sunlight should routinely wear sunblock in the phototherapy machine during treatments to prevent any reoccurrence.

When being treated, it is important not to add to the UV exposure with sunlight and sunbathing. Sun protection cream (25 SPF or higher) must be applied every 2–3 hours when outside and a wide-brimmed hat is needed on sunny days. Sunbeds are prohibited during the course of phototherapy treatment as they would increase the UV dosage and could cause severe burning.

As with exposure to natural sunlight, long-term use of UV light therapy can result in accelerated ageing of the skin (e.g. freckles and wrinkles). More importantly, there is a potential risk of developing skin cancer, in particular for PUVA phototherapy, but this is minimised by adequate dosing and treatment regimens. Your doctor will advise you on the safe total dose of UV light based on your condition and risk factors.

Is phototherapy suitable for children?

Yes, provided the child is old enough to stand in the light unit by him or herself without getting frightened. Children should visit the unit beforehand to see the light units and understand what they need to do. Initially, treatment is just for a few seconds and children quickly get used to the routine. The parent can remain by the unit and talk to the child, and sometimes there is a window they can see each other through. Parents are occasionally allowed in the unit (but fully clothed to protect their skin) for the first few treatments until the child gets used to it.

Is phototherapy the same as using a high street tanning salon?

Sunbed sessions in tanning salons are not the same as phototherapy treatments given in hospital. The high street tanning industry is unregulated – you will not know the amount of UV exposure you are receiving and your skin cancer risk will increase.

For more information on phototherapy, please see our Phototherapy factsheet