Zyrtec

What is Zyrtec used for?

Zyrtec's active ingredient, cetirizine, is a second-generation antihistamine that blocks histamine H1 receptors to reduce allergic reactions to triggers such as pollen, dust mites and pet dander, relieving sneezing, runny nose, nasal congestion, itchy eyes, hives and itchy skin. Compared with first-generation antihistamines it causes less drowsiness, and is usually taken just once a day.

How to take Zyrtec and adjust the dose

Adults and those aged 12+: typical dose is 10mg once daily. Children 6-11: 5mg once daily (or split as 2.5mg twice daily, depending on the product). Children 2-5: 2.5mg daily (once or split, per product labelling or a doctor/pharmacist's advice). Children under 2 should only use it under medical guidance. Take with water, milk or another drink, with or without food; swallow tablets whole rather than chewing. If a dose is missed, take it as soon as remembered, but do not double up. (Follow the product label or your doctor's/pharmacist's instructions for exact dosing.)

Zyrtec side effects

• Common: drowsiness (less than first-generation antihistamines but still common), headache, dry mouth, nausea, dizziness, diarrhoea (more common in children)
• Serious (rare): severe allergic reaction (facial/mouth swelling, breathing difficulty), unusual bruising or bleeding that is slow to stop

Who should not take Zyrtec?

• Contraindicated in those allergic to cetirizine, hydroxyzine, or other components
• Contraindicated/dose adjustment needed in severe renal failure
• Use with caution in epilepsy or those at risk of seizures
• Consult a doctor if you have difficulty urinating (e.g. enlarged prostate)
• Avoid alcohol while taking it, as it may increase drowsiness
• Consult a doctor if pregnant or breastfeeding