Zyrtec possible side effects

Stop taking Zyrtec and seek emergency medical attention if you experience an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives). Other, less serious side effects may be more likely to occur. Continue to take Zyrtec and talk to your doctor if you experience sleepiness, fatigue, or dizziness; headache; or dry mouth. Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.