Rebound Pruritus and Urticaria Post-discontinuation of Chronic Cetirizine Use: A Case Report.

Cetirizine is a common over-the-counter antihistamine used to treat allergic rhinitis, eczema, and urticaria. There have been increasing reports showing increased risk of rebound pruritus following discontinuation of long-term antihistamine use in the United States and the Netherlands. However, evidence on this condition and its management among Asian populations remains limited. We report the case of a Chinese male in his 50s with a background of hypertension, hyperlipidaemia, and chronic urticaria who had been regularly taking over-the-counter cetirizine for the past two years. He presented with recurrent urticaria, characterized by wheals and severe pruritus over his forearms, emerging two to three days after each cetirizine discontinuation attempt. A diagnosis of rebound pruritus and urticaria post-discontinuation of cetirizine was made. Through shared decision-making, he was switched to loratadine and chlorpheniramine for three days before transitioning to an "as-needed" regimen without recurrence of pruritus or urticaria. While the pathophysiology of rebound pruritus and urticaria post-discontinuation of chronic cetirizine use remains poorly understood, this case report suggests that the phenomenon may be drug-specific rather than a class-specific adverse effect. Larger studies are necessary to confirm if a temporary switch and short-term bridging with alternative antihistamines offer a safer discontinuation strategy for patients on chronic cetirizine.