There is currently no definitive cure for urticaria pigmentosa (UP). Psoralen plus ultraviolet A therapy is efficacious in alleviating symptoms and reducing cutaneous lesions.

The purpose of this study was to assess the effect of ultraviolet A1 (UVA1) in adult patients with UP and to compare the effectiveness of high-dose (130 J/cm²/day for 10 days) and medium-dose (60 J/cm²/day for 15 days) UVA1 radiation.

Ten and 12 adult patients with UP were treated with high-dose or medium-dose UVA1, respectively. The number of skin lesions and dermal mast cells, the presence of Darier's sign, the intensity of pruritus, and quality of life measures were evaluated before, at the end of treatment, and 2 and 6 months later.

Baseline characteristics were similar among the 2 groups of patients. In the majority of patients, the number of lesions was not significantly reduced. However, the number of mast cells in lesional skin decreased markedly in most patients by the end of treatment, and it remained low for the whole study period. Pruritus and quality of life improved considerably by the end of treatment, and the improvement was maintained during the 6-month follow up. No significant differences were observed between patients receiving high- or medium-dose UVA1.

UVA1 phototherapy ameliorates both objective and subjective symptoms of adult patients with UP and induces long-term remission in most cases. Medium-dose UVA1 appears at least as effective as high-dose UVA1.