Active Ingredient: Cetirizine Cetirizine Blocks The Action Of Histamine, Which Is Responsible For Allergy Symptoms Such As Itching, Sneezing, Runny Nose, And Watery Eyes. Zyrtec Drops Are A Liquid Form Of Cetirizine, Which Is Often Easier For Younger Children To Take. Side Effects: Drowsiness (Though Generally Mild Compared To First-Generation Antihistamines) Headache Dry Mouth Dizziness Fatigue Precautions: Consult A Healthcare Provider Before Use If You Are Pregnant Or Breastfeeding. Avoid Alcohol As It May Increase The Sedative Effects. Those With Severe Kidney Problems Should Consult A Doctor For Appropriate Dosage Adjustments. May Cause Drowsiness, So Caution Is Advised When Driving Or Operating Machinery.