• action spectrum;
  • augmentation spectrum;
  • inhibition spectrum;
  • photoallergy;
  • solar urticaria

Forty patients with solar urticaria, 16 male and 24 female, were examined personally during the past 25 years. The median age at onset of symptoms was 32 years, ranging from 13 to 76 years. Most commonly (45%) solar urticaria first appeared during the third decade. The mean duration of the disease was 3·6 years at presentation. The action spectrum was found in the visible light range in 24 patients (60%), in the ultraviolet (UV) A range in four, in the UVB in four, from the UVA to UVB in three, from the UVA to visible light in one and in a broad range from UVB to visible light in four patients. An inhibition spectrum was detected in 13 of 19 patients (68%), occurring at longer wavelengths than the action spectrum in 12 of these cases. The augmentation spectrum was found in only four of 14 patients (29%) examined. Twenty-four of 31 patients (77%) developed an urticarial reaction to autologous serum, which had been previously irradiated in vitro at the action spectrum for that patient. In a single patient, solar urticaria was caused by a drug, namely chlorpromazine. In two patients, polymorphic light eruption occurred in association with solar urticaria. No single modality of treatment was satisfactory, but combined use of antihistamines, sunbathing, psoralen UVA photochemotherapy and/or sunscreening agents partially suppressed the symptoms.