Extract

ORIGINAL ARTICLE, p 198

Idiopathic solar urticaria (ISU) is uncommon, being estimated to affect 3·9 per 100 000 population in Scotland.1 Spontaneous resolution may occur,2 but it typically persists for years.3 It can severely impair quality of life.4

Various phototherapies may be useful. ISU is diverse, with provoking wavelengths ranging from ultraviolet B (UVB) to ultraviolet A (UVA) to visible, and, even infrared rays. The wavebands used for phototherapy need not match the provoking wavebands. Narrowband (NB)‐UVB is sometimes selected to treat ISU in patients whose urticaria is triggered by longer UVA and visible wavelengths but not by UVB.5, 6 Standard NB‐UVB treatment for ISU probably works through a variety of mechanisms inducing photoprotection (hardening), as well as in other ways also relevant in chronic spontaneous urticaria.7, 8 The term ‘desensitization’, often used to describe prophylactic phototherapy for ISU, is not strictly accurate when describing standard NB‐UVB or broadband UVA monotherapy with either three‐times weekly or twice‐daily treatments.9, 10 However, using UVA in the way first described by Beissert et al.11 as ‘rush hardening’ is more akin to true ‘desensitization’ as in Hymenoptera venom immunotherapy.

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