Ultraviolet Light Therapy

Sunlight is a traditional treatment for psoriasis, as, over time, many people with the condition have found that their skin clears up in the summer months or whilst on holiday abroad. However, as with all aspects of psoriasis, this is not the rule for everybody, and there are some people who find sunlight makes their psoriasis worse.

Modern medicine has been able to pinpoint the specific part of the light spectrum that is helpful in psoriasis; ultraviolet light, and then the precise wavelength of ultraviolet light. Special molecules (chromophores) present in skin cells are able to absorb the energy from UV light, and use it to power chemical reactions that affect the function of the cells. In psoriasis, this can mean a slowing down of the multiplication of skin cells, making them behave more like normal skin.

UV therapy is one of the first treatments that a Dermatologist may prescribe, and can be used on its own or in conjunction with another treatment. UV therapy may last for anywhere between four and eight weeks, depending on the type of light treatment prescribed. Skin may be red, dry and itchy after UV therapy, and it’s therefore important to have a good moisturising regime in place. Exposure to UV light can increase the risk of developing skin cancers, which is why these treatments are so carefully monitored, and why guidelines are set as to how much UV therapy a person can have in their lifetime.

Can sunbeds help Psoriasis?

Exposure to UV light can lead to the development of skin cancers. It is important to remember that when you have UVB or PUVA treatment in a hospital, only the helpful part of the spectrum is used, and each patient’s exposure is carefully measured and monitored to stay within safety guidelines. Sunbeds are not monitored, so you do not know how much exposure you are getting, and if you are also having UV treatment it will make it impossible for the hospital to calculate the right dosage. Also, sunbeds tend to emit UVA light which, on its own, is not effective in the treatment of psoriasis.

UVB Therapy for Psoriasis

UVB Therapy has been used to treat psoriasis for decades, and is most commonly used in the treatment of guttate psoraisis or generalised plaque psoriasis. In the 1980s, the precise wavelength that was beneficial to people with psoriasis was pinpointed.  You may hear the treatment being referred to as Narrowband UVB, NBUVB or even TL01 (this is simply the type of lightbulb used).

UVB Therapy is given in a phototherapy unit in a hospital. The phototherapy team calculates how much of the UVB light each patient should be exposed to, and can increase the exposure over the course of the treatment as necessary. The treatment involves standing in a light cabinet for anything from a few seconds up to a few minutes, two to three times a week for six to eight weeks.  

PUVA Therapy for Psoriasis

UVA light is not effective for treating psoriasis on its own, and must be combined with Psoralen, to make the skin more sensitive to the UVA light. Psoralen can be taken as a tablet a couple of hours before the UVA treatment, or applied as a gel or cream onto the area to be treated. PUVA is often used to treat moderate to severe psoriasis that has not responded well to topical treatments or UVB therapy, and hand and foot machines are also available to treat pustular psoriasis.

Like UVB treatment, the psoralen and UVA dosage is carefully calculated and administered in a phototherapy unit in a hospital. Again, the treatment involves standing in a light cabinet for a few seconds or minutes, twice a week for up to eight weeks. Because the psoralen makes the body more sensitive to UVA light, people having the treatment with the tablet psoralen will have to wear special UVA-blocking glasses for around 24 hours after treatment, to prevent the formation of cataracts.

For more information, or for a list of resources used in the production of this resource, please contact the Psoriasis Association.

April 2013 (Review: April 2014)

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