Light therapy (phototherapy)

Published by Bupa's Health Information Team, March 2010.

This factsheet is for people who are having light therapy, or who would like information about it.

In light therapy (also known as phototherapy), specific wavelengths of light are used to help treat medical conditions. Different types of light therapy are useful in the treatment of many conditions, including psoriasis and other skin disorders, seasonal affective disorder and jaundice in babies. This factsheet focuses on light therapy for skin disorders.

About light therapy

It has long been known that natural sunlight can help to improve symptoms of many skin disorders, such as psoriasis and eczema. It is a part of sunlight that you can't see (called ultraviolet light) that has this beneficial effect. In light therapy, machines are used to produce ultraviolet light, which is shone on to your whole body or the area of your skin that needs treatment.

Light therapy can only be given in hospital, under the supervision of a dermatologist (a doctor who specialises in skin conditions), so your GP will need to refer you. High street sunbeds are not effective for treatment of skin disorders, as they produce a different type of light.

You will need to attend hospital two to three times a week for a course of light therapy, usually for eight to 10 weeks.

What is light therapy used for?

Ultraviolet light can help to reduce symptoms of various inflammatory skin conditions, including:

• psoriasis
• eczema
• polymorphic light eruption (PLE)
• cutaneous T-cell lymphoma (a rare type of non-Hodgkin's lymphoma)
• vitiligo

Light therapy can often completely resolve or prevent the skin problems in these conditions. However, it's not usually a permanent cure.

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).

• 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 is more intensive than broad-spectrum UVB, so treatment times are shorter.
• UVA is given together with a chemical called psoralen, which sensitises your skin to the light. Together, this is known as PUVA. PUVA is a more intensive treatment, so your doctor will usually only advise you to have it if treatment with UVB hasn't worked.

You shouldn't have PUVA if you are pregnant, and it is not suitable for children. However, UVB is suitable for both children and pregnant women.

What are the alternatives?

Your dermatologist may only suggest light therapy 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.

Depending on what you are being treated for, if light therapy doesn't work, or you are unable to have it for any reason (eg, it is not available in your area), your dermatologist may prescribe you a medicine to take instead. These medicines usually work by suppressing your immune system. However, they often have unwanted side-effects, and so are usually only given under close supervision from your doctor.

Preparing for light therapy

While you are receiving a course of light therapy, you will need to avoid additional exposure to the natural ultraviolet light in sunlight and make sure you don't put anything on your skin that can enhance the effects of the light. This means that during the course of your treatment, your doctor may advise you to:

• cover your skin when out in sunlight and not use sunbeds
• not eat too much of certain types of food 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 the 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, as some medicines can make your skin more sensitive to light.

What happens during light therapy

If you are having PUVA treatment, you will usually be given a psoralen capsule to take two hours before your UVA therapy. You may be asked to take it with a light meal. Sometimes, you may be able to use a form of psoralen added to bath water, rather than taking it as a capsule. If you have this form of therapy, you will be given the bath in hospital. In some hospitals, this is the usual way in which it is given. Psoralen can also be given as a cream or gel, if you only have small areas of skin that need to be treated.

If you are having PUVA therapy, you will be asked to wear UV protective glasses for 24 hours from when you have taken your psoralen. This is to prevent damage to your eyes, because psoralen makes your eyes, as well as your skin, more sensitive to natural sunlight.

Trained dermatology nurses or physiotherapists at the hospital will administer your light therapy. You will be asked to undress in the treatment room. If you are a man, you will be asked to keep your underpants on to protect your genital area from the ultraviolet light. You will also be given goggles to wear to protect your eyes during treatment.

The ultraviolet light is produced by specially designed cabinets containing fluorescent tubes, similar to those used in strip lighting. You will be asked to stand in the cabinet while the ultraviolet lamps are turned on.

Your doctor will work out the best dose for you to start on, based on your skin type and how easily you usually burn in sunlight. You may have a test area treated first to calculate this. In the first few sessions, your treatment may last for less than a minute. The duration may be gradually increased in later sessions, depending on how you have responded to previous doses.

What to expect afterwards

You will be able to get dressed and go home straight after your treatment. Your nurse 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 after your treatment to protect your eyes, and to make sure your skin is fully covered if you are outside or inside near a window.

What are the risks?

Light therapy is commonly performed and generally safe. However, in order to make an informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications.

Side-effects

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

The possible side-effects of light therapy include:

• redness of your skin, similar to sunburn - this should fade over the next few days, and you can use moisturisers to help relieve any discomfort
• dry and itchy skin - again, moisturises may help to relieve this
• a rash
• feeling sick with PUVA treatment - your dermatologist may suggest trying a different type of medicine or using a PUVA bath at your next session if you feel sick with psoralen tablets

Complications

Complications are when problems occur during or after the treatment.

As with natural sunlight, repeated sessions 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 doctor 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 as advised will reduce this risk.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.