A 40-year-old woman developed erythematous, raised and pruritic, migratory lesions on a daily basis affecting her whole body for the past 3 months; the appearance of the rash was consistent with urticaria. There was associated angioedema affecting her lips and face. Her medical history was significant for MS, diagnosed 9 years before, manifesting clinically with mobility, speech, and cognitive impairment. Initial treatment was with β-interferon and glatiramer acetate; however, disease relapse prompted switching to alemtuzumab, with 2 standard courses given 12 months apart (60 and 36 mg, respectively, the last dose given 12 months before the onset of rash), and achieved remission with a new baseline Expanded Disability Status Scale of 2.