Why ultra violet light may help
People with psoriasis may benefit from UVB light, one of the forms of ultra violet light that comes from the sun. There are three forms: UVA, UVB and UVC. Short wavelength UVC is absorbed by the ozone layer and does not reach the earths surface at all. The UV light which does reach us is mainly long wave UVA, with some intermediate wavelength UVB, and it is the UVB rays which may help psoriasis. UV light helps to power chemical reactions that affect the function of the cells. In psoriasis, this means that the cells do not multiply so rapidly and behave more like normal skin. Too much UVB however is not a good thing because it burns. Even UVA is not harmless and too much of both can prematurely age the skin and increase the risk of skin cancer. You really do need to take care even if you do find that sunshine helps your skin. You are at highest risk if you are fair or red haired and your skin does not tan easily. Because ultra violet light is so effective for so many people with psoriasis doctors use it in various artificial forms. The British Photodermatology Group is an advisory group on the use of UV light in the UK.What is UVB treatment?
UVB contains a wide range of wavelengths and is used to treat guttate psoriasis or plaque psoriasis, which is resistant to topical treatments (i.e creams and ointments). In the past few years a more defined form of UVB has been developed, known as 'narrow band', and this is proving effective. The aim is to clear the skin and this can take up to 30 treatments over a period of weeks. This treatment is administered in hospital under controlled conditions using trained staff.What is PUVA?
This is a light treatment using a psoralen and UVA treatment. UVA on its own is not active in skin disease but if given with a psoralen, which makes the skin more sensitive to light, it can be very effective. Psoralen is derived from plants and is normally taken as a tablet or sometimes in a bath. There are three groups of people who will be considered for PUVA treatment:-people with severe psoriasis that is not responding to topical treatments, people whose psoriasis returns within three to six months of successful treatment as in -patients or day patients, people who do not want topical treatment and for whom UVB has failed. Like UVB treatment this is administered in hospital under controlled conditions using trained staff.
