Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop using levocetirizine and call your doctor at once if you have:
worsening allergy or urticaria symptoms;
painful or difficult urination;
little or no urination;
a light-headed feeling, like you might pass out;
fever; or
signs of an ear infection--ear pain or full feeling, trouble hearing, drainage from the ear, fussiness in a child.
Common side effects may include:
drowsiness, tiredness;
sinus pain;
ear infection;
cough;
fever;
nosebleed;
vomiting, diarrhea, constipation;
dry mouth; or
weight gain.
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.
 Levocetirizine side effects (more detail)
