An investigator-blinded, randomized study enrolled 109 patients (mean age 49 years) with psoriasis to either a suberythematogenic (n = 54) or erythematogenic (n = 55) UVB irradiation regimen. Itching and scratching at baseline were assessed as predictors of time to clearance of psoriasis. Clearance was defined as a reduction of 90% in the Psoriasis Area and Severity Index (PASI) at baseline. This was assessed at baseline and every 4 weeks; itching and scratching was assessed at baseline using the Impact of Skin Disease on Daily Life (ISDL). Seventy-seven patients (70.6%) achieved psoriasis clearance, but there was no significant difference in the percentage of patients achieving clearance between the two groups (74.5 vs. ...