Ultraviolet light can be used to treat psoriasis and has been used for many years. Over this time, the process has been improved to give a safer and higher quality treatment. This form of light treatment is not the same as that used in tanning beds.

After a course of light therapy (also known as phototherapy), the amount of time the skin remains improved can vary; for some people it lasts for a few weeks and for others several months. There are 2 different types of light therapy used in clinic: PUVA and UVB.

PUVA

PUVA is a treatment that combines Psoralen and UVA (ultraviolet A) light. UVA causes a reaction in the skin but it doesn’t improve psoriasis on its own, psoralen has to first make the skin cells sensitive. Psoralen is usually taken as a tablet but can also be applied directly to the skin before exposure to the UVA.

UVB

UVB (ultraviolet B) is used on its own but only part of the UVB energy (light) band has an effect on psoriasis. In light treatment, the rest of the UVB energy that is not needed but may cause harm has been filtered out. So sometimes, you will hear UVB treatment called ‘narrowband’ or ‘TL01’.

Light therapy may be used if topical treatments have not been able to control your psoriasis sufficiently or if your psoriasis is on lots of places on your body.

The treatment can only be arranged by a specialist skin doctor (dermatologist). If necessary, it may be used in combination with other treatments.

How does it work?

It is not entirely clear how light therapy helps improve psoriasis. It is likely that two things are happening. The treatment:

1. causes some changes in skin cells that stops them growing so quickly and;
2. alters the activity of some local immune system cells (called lymphocytes) in the skin.

Because UV light alters cell activity and damps down the local immune system there may be a risk of skin cancer in the long-term. Light treatment at the clinic is filtered to reduce the damaging effects and exposure is monitored carefully. Sunbathing and sunbeds in particular are more of a risk as more of the damaging light reaches the skin.

Before you start on light therapy, you will be given different doses of light to small patches of your skin. How your skin reacts in those small patches will decide what strength of treatment is needed to make the light effective and keep you safe.

Sunbeds

Tanning sunbeds are not a good idea for treating psoriasis. They mainly give out UVA light. This light causes tanning but also is the light that mostly damages the skin. It doesn’t have much of an effect on psoriasis on its own. Any improvements you may see are most likely due to a tan disguising the appearance of your psoriasis.