Dr Gnanapavan at Barts just wrote this. The TL;DR is: The saying where there is fire there is smoke is an apt descriptor of drug-related side effects. In a letter to the editor, following a similar report on the topic the authors report a case of acute ofatumumab-induced urticaria (see Figure below). It was easily treated with anti-histamines, and further injections were taken together with antihistamines without problems. <img> Figure: Image taken from the case report showing multiple erythematous wheels. The case underscores the importance of monitoring for potential skin reactions with ofatumumab, particularly in those with a history of urticaria. It is a known class effect with anti-CD20s, for example, with ocrelizumab and rituximab. If problematic desensitisation to the allergy can be considered. Mult Scler. 2024 Aug 26:13524585241273084. The whole article is here: https://multiple-sclerosis-research.org/2024/08/urticaria-following-ofatumumab/