Cases reported to the FDA Adverse Events Reporting System were rare (209 worldwide reports over >6 years), but many of them described severe pruritus requiring medical intervention that occurred within a few days of stopping cetirizine or levocetirizine. Most cases occurred after more than 3 months of daily use, but some occurred after less than one month. The mechanism of the effect is unknown.

Restarting the antihistamine improved pruritus symptoms in most patients; subsequently tapering off the drug resolved symptoms in some of these patients.

Whether switching to another antihistamine, such as loratadine (Claritin, and others) or fexofenadine (Allegra, and others), would prevent or improve pruritus or whether these drugs could carry a similar risk after their discontinuation is unknown. Some expert clinicians have prescribed (off-label) the interleukin-4 receptor alpha antagonist dupilumab (Dupixent) or the recombinant anti-IgE monoclonal antibody omalizumab (Xolair, and biosimilar), both of which are FDA-approved for treatment of chronic spontaneous urticaria,2,3 for treatment of patients whose symptoms persist following taper and discontinuation of cetirizine or levocetirizine.