Antihistamines, one of the main types of allergy medicine, can be safe to use after the expiration date. For over-the-counter medicines like Claritin and Zyrtec, the listed expiration dates are typically around two and a half years after manufacturing.

How long will cetirizine last?

Response and effectiveness. Peak concentrations are reached within one hour of administration of cetirizine tablets or syrup. The onset of effect occurs within 20 minutes in 50% of people and within an hour in 95%. Effects persist for at least 24 hours following a single dose of cetirizine.

Is it OK to take expired allergy medicine?

It may be fine to take an allergy medication that's a month past its expiration date. But there is some risk in taking a heart rhythm medication that, if ineffective, could lead to an unstable and dangerous heart problem.