Cetirizine — what it does and when to use it

Cetirizine is a popular antihistamine people reach for when sneezing, itchy eyes, runny nose, or hives show up. It blocks histamine, the chemical your body releases during an allergic reaction. Most adults feel relief within an hour, and one normal dose usually lasts about 24 hours. That's why many take it once a day.

How to take cetirizine

For adults the common dose is 10 mg once daily. Some people split it to 5 mg twice a day if 10 mg feels too strong. Take it with or without food at the same time each day to keep things consistent. If you miss a dose, skip it and take the next dose at the usual time—don't double up.

Kids' doses vary by age and weight. Always follow the product label or your doctor’s instructions. If you care for a child, check the medicine’s age range and dosing device—do not guess the dose.

What to watch for — side effects and safety tips

Cetirizine is a second-generation antihistamine, so it causes less drowsiness than older drugs, but some people still feel sleepy or foggy. Other common effects include dry mouth, headache, and mild stomach upset. If you feel very sleepy, avoid driving or using heavy machinery until you know how it affects you.

Talk to your doctor if you have kidney problems. Cetirizine is cleared by the kidneys, and doctors often lower the dose for people with reduced kidney function. If you're pregnant, breastfeeding, or on other medicines, check with a healthcare professional before starting cetirizine.

Mixing cetirizine with alcohol or strong sedatives can increase drowsiness. Also tell your doctor about other medicines that depress the central nervous system so they can advise you.

Want a quick comparison? Loratadine and fexofenadine are the main alternatives. They also work once a day and tend to cause minimal drowsiness. People respond differently—if cetirizine makes you sleepy, try one of those after talking to your provider.

If your allergy symptoms suddenly get worse or you develop swelling, breathing trouble, or a rash that spreads quickly, get medical help right away. For ongoing or severe symptoms, a doctor can check whether antihistamines alone are enough or if you need nasal sprays, eye drops, or allergy testing.

Buying tips: choose a licensed pharmacy, read labels, check expiry dates, and avoid suspiciously cheap or unverified sites. Over-the-counter brands and generics contain the same active ingredient. If you order online, be sure the pharmacy shows clear contact info and verified credentials.

Short and practical: cetirizine is an effective, once-a-day option for many allergy sufferers. Use the right dose, watch for drowsiness, adjust for kidney issues, and ask a clinician when in doubt. That keeps relief steady and safe.