Ultra violet light therapy

Why ultraviolet light may help
Approximately 80% of people with psoriasis notice an improvement in their skin after they have been in the sunshine. The use of the sun’s rays has been used to treat psoriasis for over a century, however, of the ultraviolet rays emitted by the sun, only UVA and UVB is of benefit to people with psoriasis.
UV light helps to power chemical reactions that affect the function of skin cells. In psoriasis, this means that the skin cells do not multiply so rapidly, and behave more like normal skin.

What is UVB treatment?
Since the 1920’s, UVB (280-320nm) has been artificially used to treat guttate and generalised plaque psoriasis that has not responded to topical treatments, or is particularly widespread. In 1981 the precise wavelength of UVB that is of benefit to people with psoriasis was discovered, this lies between 300-313nm. Since this discovery UVB treatment has been developed based on the narrowband of 311-313nm, using the Phillips TL-01 lamp. You may therefore hear of UVB treatment being referred to as Broadband UVB (BBUVB) or Narrowband UVB (NBUVB or TL-01).
This type of treatment is given in a phototherapy centre and administered by a team of health professionals. Your dermatologist will calculate precisely how much UVB light your skin should be subjected to, and will increase the exposure accordingly.
Treatment is usually given two or three times a week, for a period of four to six weeks. You will need to stand in the UVB cabinet for a period of a few seconds to several minutes.

What is PUVA treatment?
PUVA was introduced in the 1970’s. UVA (320-400nm) is not beneficial in treating psoriasis on its own; instead it must be combined with Psoralen (P). A chemical, derived from plants, Psoralen is required in order to make the skin more sensitive to the UVA light. Psoralen can be taken as a tablet (two hours before treatment with UVA), or applied externally to the skin as a gel or cream (30 minutes before treatment with UVA). Another option is to add the psoralen to bath water and soak in the bath for 10-15 minutes.
Since 1970, PUVA has been used to treat moderate to severe plaque psoriasis that has not responded to topical treatments, or UVB therapy. PUVA can be more successful on thicker plaques of psoriasis than UVB, as the UVA is absorbed much deeper in the skin. Hand and foot PUVA machines are also used to treat palmar-plantar pustular psoriasis.
Like UVB, PUVA is given in a phototherapy centre and administered by a team of health professionals. Your dermatologist will calculate precisely how much Psoralen and UVA your skin requires, and will increase your exposure to the UVA light accordingly.
Treatment is usually given twice a week, for a period of five to eight weeks. You will need to stand in the UVA cabinet for a period of a few seconds to several minutes.
If you are taking a tablet form of Psoralen you will need to wear special UVA blocking eye protection for 12 to 24 hours after you have taken the tablet. Psoralen makes not only the skin more sensitive to UVA, but also the eyes and so UVA-blocking glasses must be worn in order to prevent the formation of cataracts. The glasses must be worn anywhere the sun shines – even indoors as UVA, unlike UVB can penetrate through glass. You should look for sunglasses marked UV400 as the lenses in these glasses block all wavelengths below 400nm (i.e. UVA and UVB).

What are the risks / side effects?
· Exposure to UV light (A or B) can cause skin damage, premature ageing and increases the risk of skin cancer. For these reasons, the British Photodermatology Group have issued guidelines as to the total number of UV treatments an individual can have in a lifetime.
· Some redness of the skin and subsequent tanning is likely, but you should let the staff in the department know if you experience any burning sensations (usually 12-24 hours after treatment).
· UV treatment can cause the skin to become dry and subsequently itchy – apply plenty of moisturiser in order to overcome this. However, if the itching worsens, do tell the phototherapy nurse or dermatologist.
· The Psoralen tablet can make you feel sick – if you experience this, do mention it to the dermatologist as they may be able to change the type of Psoralen, or prescribe a tablet to stop you feeling sick.

Sunbeds, sunlamps and natural sunlight
UV treatment in hospital is very carefully controlled and using a sunbed outside the hospital setting makes it difficult to ensure that you are receiving the correct dose. Pure UVA sunbeds are also ineffective for the treatment of psoriasis.
It is still important to follow sun safety advice even if your psoriasis improves in the sunshine so as to prevent the potential side effects such as skin cancer and premature ageing. Sunburn can actually aggravate psoriasis, so do use a suncream with an SPF of 15 or above and re-apply it regularly. Aim to cover up with a hat, t-shirt and sunglasses, and avoid being out in the hot sun between 11am and 2pm.

This is a brief description of Ultra Violet Light; there is ongoing research into the subject - for additional information contact the Psoriasis Association.