Phototherapy is a treatment used at Great Ormond Street Hospital (GOSH) for severe psoriasis. There are two main types of phototherapy: UVB and PUVA.
The 'P' in PUVA stands for Psoralen. Psoralens are a group of chemicals which are found in certain plants, fruit and vegetables. UVA is a type of light. When UVA light and psoralens are used together they stop the skin cells from multiplying too quickly (which is what happens when you have psoriasis).
Your doctor is unlikely to suggest this treatment unless you have tried special creams for psoriasis first (such as corticosteroids and tar applications).
You will usually have to visit the hospital twice a week for treatment and this will continue for five to eight weeks.
You may be given the psoralen as a pill two hours before you have the UVA light treatment. Some people find they feel a bit sick after taking these pills so it is a good idea to have them with a light meal or a glass of milk.
Otherwise you may have psoralen solution added to a bath (which you will have to lie in for 10-15 minutes) or a psoralen cream or gel.
You will have to wear eye protection goggles and then you will need to stand in a PUVA cabinet (which is a bit like a standing sunbed). It has fluorescent tube lighting that is very bright. The psoralen makes your skin more sensitive to UV light and this should help your psoriasis.
How long it takes depends on whether you will be having the bath, gel or pill form of the psoralen. The UVA part of the treatment won’t take very long. At first you will only have a few minutes and this will gradually be increased (20-30 minutes is the maximum). The amount of time spent in the light will depend on how dark your skin is.
Does it hurt?
PUVA treatment may make your skin burn a little (like sunburn). However, this burn may take longer to disappear than usual (from two days to one week). The psoralen may make you feel a bit sick, if this is the case tell your doctor as the type of psoralen can be changed. The actual light treatment should be painless. Your skin may feel dry and itchy afterwards, though moisturisers should help this.
Since the psoralen makes your skin more sensitive you will need to be careful during the course of treatment.
- Wear eye protection. For 24 hours after taking the psoralen tablets you will need to wear sunglasses with UVA protection. If you do not know whether your sunglasses have UVA protection, take them to the hospital where they can be tested. You do not have to wear them indoors unless there is a lot of natural sunlight in the room.
- Underwear should be worn (especially by males) in the PUVA cabinet.
- Don’t sunbathe. During the course of treatment don’t sunbathe or use sunbeds. Try to avoid sunlight on treatment days.
- Moisturisers. Some moisturisers have sun protection filters in them. This will make the treatment less effective. Check with your doctor if you are unsure
- Avoid perfume and aftershaves on treatment days as this could cause a skin reaction.
What about skin cancer?
There is a slightly higher risk of skin cancer with the use of this treatment. But the risk is still thought to be low for short courses of treatment. It is not recommended to have long-term PUVA treatment. Long-term treatment may also age your skin.
Make sure that you tell your dermatologist if you are on any medications. Some medicines can make your skin burn more easily so it is really important that they know to expect this.
Last reviewed: November 2011