Get emergency medical help if you have signs of an allergic reaction to Zyrtec: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Stop taking this medicine and call your doctor at once if you have:
fast, pounding, or uneven heartbeat;
weakness, tremors (uncontrolled shaking), or sleep problems (insomnia);
severe restless feeling, hyperactivity;
confusion;
problems with vision; or
little or no urination.
Common Zyrtec side effects may include:
drowsiness, tiredness;
dizziness, feeling light-headed;
feeling hot, sweating;
numbness, tingling, burning pain;
decreased sense of taste;
headache;
upset stomach, nausea, constipation; or
dry mouth, sore throat.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Zyrtec side effects (more detail)
