Cetirizine
Over-the-counterWhat is Cetirizine?
Cetirizine is an over-the-counter antihistamine medication used to treat allergy symptoms. It belongs to a class of drugs called second-generation antihistamines. These medications work by blocking histamine, a substance your body makes during an allergic reaction.
You may know cetirizine by its brand name Zyrtec. It comes in tablets, liquid-filled capsules, chewable tablets, and liquid syrup forms. Cetirizine is considered a non-drowsy antihistamine, though some people still experience drowsiness. It provides 24-hour relief from seasonal and year-round allergies with just one daily dose.
Unlike older antihistamines, cetirizine is less likely to cross into your brain. This means it causes less drowsiness for most people. It starts working within 20 to 60 minutes after you take it. The effects last for a full day, making it convenient for daily allergy management.
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Common uses
- Seasonal allergic rhinitis, also called hay fever, with symptoms like sneezing and runny nose
- Year-round allergic rhinitis caused by dust mites, pet dander, or mold
- Chronic idiopathic urticaria, which means hives with no known cause
- Itchy, watery eyes from environmental allergies
- Allergic skin reactions including itching and redness
- Relief from indoor and outdoor allergy triggers
How it works
When you encounter an allergen like pollen or pet dander, your immune system releases histamine. Histamine attaches to receptors in your nose, eyes, skin, and other tissues. This causes the classic allergy symptoms you experience, including sneezing, itching, swelling, and mucus production.
Cetirizine blocks histamine from attaching to H1 receptors in your body. By preventing histamine from binding to these receptors, cetirizine stops allergy symptoms before they become bothersome. It does not cure allergies or prevent your body from making histamine. Instead, it blocks histamine's effects so you feel relief from symptoms.
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Dosage information
Adults and children 6 years and older typically take 5 to 10 mg once daily. Children ages 2 to 6 years usually take 2.5 to 5 mg once daily. Children ages 6 months to 2 years may take 2.5 mg once daily. The maximum recommended dose for adults is 10 mg in 24 hours. You can take cetirizine with or without food. If you experience drowsiness, taking it at bedtime may help. Always follow the dosing instructions on the package or your doctor's recommendations.
Side effects
- Drowsiness or feeling tired, even though it is marketed as non-drowsy
- Dry mouth
- Headache
- Stomach pain or nausea
- Dizziness
- Sore throat
Serious side effects are rare but can include severe allergic reactions, difficulty urinating, or vision problems. Stop taking cetirizine and seek medical help if you experience difficulty breathing, severe dizziness, or fast or irregular heartbeat. Contact your doctor if side effects become bothersome or do not go away.
Drug interactions
- Alcohol may increase drowsiness and dizziness when combined with cetirizine
- Other antihistamines or cold medications may increase side effects
- Sedatives, sleep aids, or anti-anxiety medications may cause excessive drowsiness
- Muscle relaxants may increase drowsiness and dizziness
- Opioid pain medications may enhance sedative effects
- People with kidney disease may need a lower dose because cetirizine is removed through the kidneys
- Avoid driving or operating machinery until you know how cetirizine affects you
Blood test monitoring
Cetirizine does not typically require routine blood test monitoring for most people. However, if you have kidney disease, your doctor may want to check your kidney function with blood tests before starting cetirizine. Tests like creatinine and estimated glomerular filtration rate, known as eGFR, measure how well your kidneys filter waste. These tests help your doctor determine the right dose for you. If you develop unusual symptoms or take cetirizine for extended periods, your doctor may recommend periodic kidney function tests. People with liver disease may also benefit from liver function monitoring, though cetirizine is primarily removed through the kidneys.
Related blood tests
Taking Cetirizine? Monitor your levels.
- Track how your body responds
- Catch side effects early with blood work
- Share results with your doctor
Frequently asked questions
Cetirizine is available over the counter without a prescription. You can purchase it at Rite Aid and most pharmacies under the brand name Zyrtec or as a generic option. Prescription-strength cetirizine exists but contains the same 10 mg dose available over the counter. The generic version costs less and works exactly the same as the brand name.
Cetirizine typically starts working within 20 to 60 minutes after you take it. Most people notice relief from allergy symptoms within one hour. The medication reaches peak effectiveness about one hour after taking it and continues working for 24 hours. For best results, take it at the same time each day during allergy season.
You can take cetirizine every day for ongoing allergy management or only when you have symptoms. Daily use during allergy season provides consistent symptom control and may work better than taking it as needed. Many people take it daily during spring and fall when pollen counts are high. Talk to your doctor if you need to take cetirizine daily for more than 6 months.
Cetirizine causes less drowsiness than older antihistamines like diphenhydramine. However, drowsiness still affects about 10% of people who take it. It is considered a non-drowsy antihistamine, but individual responses vary. If you feel drowsy, try taking it at bedtime instead of in the morning.
Cetirizine is generally safe to combine with most medications. However, avoid taking it with other antihistamines or cold medications that contain antihistamines to prevent doubling up. Be careful combining cetirizine with alcohol, sleep aids, or sedatives as these increase drowsiness. Always check with your pharmacist or doctor about your specific medications before starting cetirizine.
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue your regular schedule. Never take two doses at once to make up for a missed dose. Missing an occasional dose will not harm you, but your allergy symptoms may return.
Most healthy people do not need blood test monitoring while taking cetirizine. However, people with kidney disease should have their kidney function checked before starting cetirizine and periodically during treatment. Rite Aid offers blood testing that measures kidney markers like creatinine and eGFR. These tests help ensure cetirizine is safe for you and that you are taking the right dose.
Yes, cetirizine is approved for children as young as 6 months old. The dose depends on the child's age and weight. Children 6 months to 2 years take 2.5 mg once daily, children 2 to 6 years take up to 5 mg daily, and children 6 years and older can take the adult dose of 10 mg. Always use the measuring device that comes with liquid cetirizine to ensure accurate dosing.
Cetirizine is a second-generation antihistamine that causes less drowsiness than older options like diphenhydramine. Compared to other second-generation antihistamines like loratadine and fexofenadine, cetirizine works faster but may cause slightly more drowsiness. It provides 24-hour relief with once-daily dosing. Some people respond better to one antihistamine than another, so you may need to try different options.
Cetirizine is generally considered safe during pregnancy and is often recommended as a first-choice antihistamine. However, you should always talk to your doctor before taking any medication while pregnant. Small amounts of cetirizine pass into breast milk, but it is usually considered compatible with breastfeeding. Your doctor can help you weigh the benefits and risks for your specific situation.