The U.S. Food and Drug Administration (FDA) has issued a warning about a rare but serious side effect: severe itching after long-term use of the oral antihistamines cetirizine (Zyrtec) and levocetirizine (Xyzal) is discontinued. This symptom, which may appear days after stopping the daily use of these medications for months or even years, has been reported in patients who had not experienced itching before treatment.

Between April 2017 and July 2023, more than 200 global cases of severe itching following the discontinuation of these antihistamines were documented. Although this number is relatively low compared to the more than 60 million units sold in 2022 alone, the severity of the symptom has prompted the FDA to update prescription information and request that over-the-counter manufacturers include warning labels on their products.

Post-discontinuation itching can be so intense that it interferes with sleep and daily activities, and in some cases, symptoms improve when the medication is resumed. The FDA recommends that patients who experience severe itching after stopping cetirizine or levocetirizine consult their healthcare provider.

This phenomenon is not exclusive to these antihistamines. In 2020, the FDA issued a black box warning for montelukast (Singulair) due to risks of neuropsychiatric side effects, including suicidal thoughts.

Given that over 100 million Americans suffer from some form of allergy, it is essential that both patients and healthcare professionals are informed about these risks. The FDA emphasizes the importance of discussing the benefits and risks of long-term antihistamine use and of avoiding abrupt discontinuation without medical supervision.

This warning highlights the need for ongoing vigilance and open communication between patients and healthcare providers to ensure the safe and effective treatment of allergies.