A controlled study of ultraviolet A sunbed treatment of psoriasis

Ultraviolet (UV) A sunbeds are widely used by patients with psoriasis in an attempt to treat their skin disease. However, there is little evidence that UVA therapy improves psoriasis, and the long-term risks of sunbed exposure are not known.

To perform a randomized, placebo-controlled study of UVA sunbed therapy for psoriasis.

A sunbed and canopy unit was modified to allow UVA exposure on one side of the body (front and back), and 'placebo' visible light exposure on the other side of the body. We treated 38 patients with psoriasis, giving 12 exposures over a period of 4 weeks. Assessment was made using a modified Psoriasis Area and Severity Index (PASI) score, individual plaque assessment and patient questionnaire.

In 17 patients (47%) the PASI score showed a greater reduction on the UVA side compared with placebo, in 11 patients (31%) no difference was recorded between the two sides, and in eight (22%) the improvement was greater on the placebo-treated side. Overall, the median pretreatment half-body modified PASI score was 4.4 units, reducing to 3.9 units on the UVA-treated side and 4.2 units on the placebo-treated side (P = 0. 044 for difference in response). Breakdown of the plaque score into the individual components of erythema, scale and thickness revealed significant improvement only with the score for erythema. Although the degree of improvement was small, 64% of patients felt that the response was sufficiently good that they would use a sunbed again to treat their psoriasis.

Our results show that a short course of sunbed treatment does improve psoriasis in some patients, but that the degree of improvement is small.