Cetirizine: What It Treats and How to Use It Safely

Sneezing, itchy eyes, runny nose or hives can ruin your day. Cetirizine (often sold as Zyrtec) is a common over-the-counter antihistamine many people use to calm those allergy symptoms. It’s popular because one pill usually works for the whole day and it’s easy to take.

How cetirizine helps

Cetirizine blocks histamine, the chemical your body releases during an allergic reaction. That reduces sneezing, itching, watery eyes, and skin hives. People use it for seasonal hay fever, indoor allergies (dust, pet dander), and chronic urticaria (ongoing hives).

How to take cetirizine

Adults and kids 6 and older: the usual dose is 10 mg once daily (one tablet or teaspoon of syrup). For children 2–5 years, follow the specific syrup dose on the label or your doctor’s advice. Take it at the same time each day for steady relief. You can take it with or without food.

It usually starts working within an hour and lasts about 24 hours. If one dose doesn’t help, don’t double up—talk to your pharmacist or doctor about other options.

If you have kidney problems, doctors often lower the dose. Older adults may also need a lower dose to avoid extra drowsiness or confusion.

Pregnant or breastfeeding? Talk to your clinician before using cetirizine. Many providers prefer to discuss benefits and risks first.

Side effects and safety tips

Most people tolerate cetirizine well. Common side effects are mild: drowsiness for some users, dry mouth, headache, or slight stomach upset. If you feel very sleepy, avoid driving or using heavy machinery until you know how it affects you.

Avoid drinking alcohol or using other sedating medicines with cetirizine—those combinations boost drowsiness. Also mention cetirizine to your prescriber if you take antidepressants or medicines that affect the nervous system; there can be interactions.

Stop and call a doctor if you get fast heartbeats, severe dizziness, trouble breathing, or swelling—those are signs of a serious reaction and need urgent care.

Compare it briefly: loratadine (Claritin) is less likely to cause drowsiness for some people, while levocetirizine is a stronger version of cetirizine used when normal doses don’t help. Your choice depends on symptoms, side effects, and what your doctor recommends.

Storage and buying tips: store tablets in a cool, dry place and check expiration dates. You can buy cetirizine OTC in most places, but if symptoms persist despite regular use, see a doctor—there might be other causes or better treatments.

Bottom line: cetirizine is a simple, effective option for many allergy sufferers. Use the right dose, watch for drowsiness, and check with a clinician if you’re pregnant, elderly, or have kidney issues.