8 Zyrtec Side Effects You Should Know About
Key takeaways:
Zyrtec (cetirizine) is a popular antihistamine that’s usually well tolerated. Most Zyrtec side effects are mild and easily managed at home. Common Zyrtec side effects include drowsiness, dry mouth, and sore throat.
Other possible Zyrtec side effects include nausea, stomach pain, and diarrhea. Severe itching may also appear after you stop taking Zyrtec, especially if you’ve been taking it long-term.
Rare but serious Zyrtec side effects include mood or behavior changes and liver problems. These aren’t common, but they require medical attention if they occur.
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Table of contents
Zyrtec (cetirizine) is an antihistamine that treats allergies. It’s available both over the counter (OTC) and with a prescription, and it’s generally well-tolerated. But as with any medication, there are some potential side effects to know about.
Here, we’ll review common and rare Zyrtec side effects and how to manage them if they occur.
Zyrtec side effects at a glance
Below are the mild and serious Zyrtec side effects reported in clinical studies. Keep in mind that everyone responds differently to medication. So it’s best to reach out to a healthcare professional if you experience any concerning side effects while taking Zyrtec, even if they aren’t listed here.
Mild Zyrtec side effects include:
Drowsiness
Headache (more common in children)
Sore throat
Stomach pain
Fatigue
Diarrhea
Dizziness
Dry mouth
Nose bleeds
Nausea and vomiting
Cough
Rare Zyrtec side effects include:
Severe itching after stopping Zyrtec
Bronchospasm (trouble breathing)
Trouble peeing
Blurred vision
Hearing problems
Mood or behavior changes
Movement disorders
Seizures
Very low blood pressure
Liver problems
Below, we’ll go into more detail about eight Zyrtec side effects and how to manage them.
1. Drowsiness
Feeling drowsy is a common Zyrtec side effect. It’s typically not as severe as the drowsiness caused by first-generation antihistamines, such as diphenhydramine (Benadryl). But it can be bothersome for some people. It’s best to avoid driving or other activities that require alertness until you know how Zyrtec affects you.
Drowsiness seems to be a dose-related side effect. Lowering your Zyrtec dosage may help you manage this side effect. Taking Zyrtec in the evening is another option if daytime drowsiness is bothersome for you.
How long does it take Zyrtec to work? Read a pharmacist’s answers to this, as well as more Zyrtec FAQs.
Benadryl vs. Zyrtec: Here’s how these two antihistamines compare.
The best nondrowsy antihistamines: Learn which allergy medications are less likely to make you sleepy.
If drowsiness persists or it’s interfering with your ability to perform daily tasks, talk to your pharmacist or prescriber about a non-drowsy allergy treatment. Allegra (fexofenadine) and Claritin (loratadine) are both effective OTC options.
2. Dry mouth
Dry mouth can be a side effect of antihistamines. It’s more common with first-generation antihistamines, but it can happen with newer antihistamines, such as Zyrtec, too. Dry mouth seems to increase as the Zyrtec dosage goes up. So lowering your dose may help resolve it.
You can help counteract dry mouth by sipping on water throughout the day, chewing sugar-free gum, or using a saliva substitute spray. If you’re taking Zyrtec long term and it’s causing dry mouth, it’s also a good idea to stay on top of your dental appointments. Over time, dry mouth can lead to tooth decay without proper dental care.
3. Sore throat
Sore throat is another possible Zyrtec side effect. It may be related to dry mouth, since producing less saliva can also leave your throat feeling dry and make it more painful to swallow. But keep in mind that allergies can also cause a sore throat due to post-nasal drip.
You can soothe a sore throat with a salt water gargle. Staying hydrated can also help. If needed, an OTC pain medication, such as Advil (ibuprofen) or Chloraseptic spray, may also help. Just make sure your healthcare team OKs it.
If you have other allergy symptoms along with a sore throat, it could be a sign that Zyrtec isn’t working well for you. If you have a fever or swollen lymph nodes in your neck along with a sore throat, it’s best to seek medical care. You could have an infection that requires treatment.
4. Nausea
Nausea isn’t common with Zyrtec, but it happens for some people taking it. Children also reported stomach pain in clinical studies. You can take Zyrtec with or without food. But if it’s making you nauseous, taking it with food may help. Just be sure to avoid spicy or greasy foods, as they can worsen nausea.
If your nausea worsens or doesn’t improve, talk to your pharmacist or prescriber about a different treatment option for your allergy symptoms.
5. Diarrhea
Diarrhea is another possible Zyrtec side effect. It seems to be more common in children taking Zyrtec than in adults.
Diarrhea may improve over time as your body adjusts to the medication. Be sure to drink fluids to avoid dehydration if you have diarrhea.
If needed, an OTC medication, such as Imodium A-D (loperamide) or Pepto-Bismol (bismuth subsalicylate), may help manage your diarrhea. But if it continues for more than a few days, or becomes severe, talk with a healthcare professional. They can make sure there isn’t a more serious cause of your symptoms.
6. Severe itching after stopping Zyrtec
You may experience severe itching after you stop taking Zyrtec. This is more likely if you’ve been taking it on a daily basis for several months or longer. But it’s also possible after less than 1 month of regular use.
Slowly tapering Zyrtec over time instead of stopping it abruptly may help reduce this side effect. But if you experience severe itching after you stop taking it, talk to your healthcare team for guidance. And do your best to avoid scratching, since it can raise the risk of infection and may even make itching worse.
7. Mood changes
While less common, Zyrtec can sometimes cause mood changes, such as agitation, anxiety, or mood swings. Hallucinations and suicidal thoughts can also happen in rare cases.
If you notice a change in your behavior (or your child’s) after taking Zyrtec, it’s best to stop taking it and seek medical care. If thoughts of self-harm are involved, emergency care is recommended.
If you or someone you know is having thoughts of suicide, you’re not alone, and help is available. Call the National Suicide Prevention Lifeline at 988, or text “HOME” to 741-741 to reach the Crisis Text Line.
8. Liver problems
In rare instances, some people have reported liver problems while taking Zyrtec. This isn’t common, and in most cases it will resolve once you stop taking Zyrtec.
Signs and symptoms of liver damage include:
Stomach pain
Yellow-colored skin or eyes (jaundice)
Dark-colored urine
Swollen stomach
If these symptoms appear while you’re taking Zyrtec, seek medical care as soon as possible.
Frequently asked questions
It’s possible. Histamine plays a role in regulating appetite and body weight. Zyrtec blocks histamine to control allergy symptoms. But this may have a negative effect on the body’s ability to regulate weight, leading to weight gain over time. Weight gain from Zyrtec and other second-generation antihistamines doesn’t seem to be an issue with short-term use. But if you’re taking Zyrtec long term, talk to a healthcare professional about any concerns about its effect on your weight.
Both increased and decreased blood pressure were reported in clinical studies of Zyrtec. But these aren’t common Zyrtec side effects. Zyrtec is considered a safe medication to take if you have high blood pressure (hypertension). Just be sure to avoid Zyrtec-D, as it contains a decongestant (pseudoephedrine) along with Zyrtec. Zyrtec-D can raise your blood pressure and isn’t recommended if you have hypertension.
The bottom line
Zyrtec (cetirizine) is a popular antihistamine that treats allergy symptoms. It’s typically a well-tolerated medication, and many people may not experience any side effects while taking Zyrtec. Most side effects that occur are mild and easily managed at home.
Common Zyrtec side effects include drowsiness, dry mouth, and sore throat. Nausea, stomach pain, and diarrhea can also happen in some cases. Severe itching may also appear after you stop taking Zyrtec, especially if you’ve been taking it long-term. Taking Zyrtec long term may also increase your chance of weight gain.
Rare but serious Zyrtec side effects include mood changes and liver problems. Seek medical care if these side effects occur.
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References
Church, M. K., et al. (2013). Pharmacology of antihistamines. Indian Journal of Dermatology.
LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. (2017). Cetirizine. National Institute of Diabetes and Digestive and Kidney Diseases.
MedlinePlus. (2024). Dry mouth.
Naqvi, A., et al. (2024). Cetirizine. StatPearls.
National Institute of Dental and Craniofacial Research. (2024). Dry mouth. National Institutes of Health.
Ozdemir, P. G., et al. (2014). Assessment of the effects of antihistamine drugs on mood, sleep quality, sleepiness, and dream anxiety. International Journal of Psychiatry in Clinical Practice.
Preferred Pharmaceuticals. (2025). Cetirizine hydrochloride solution [package insert].
Provensi, G., et al. (2016). The histaminergic system as a target for the prevention of obesity and metabolic syndrome. Neuropharmacology.
PubChem. (2009). Cetirizine. National Library of Medicine.
Rupert, J., et al. (2022). Pruritus: Diagnosis and management. American Family Physician.
U.S. Food and Drug Administration. (2025). FDA requires warning about rare but severe itching after stopping long-term use of oral allergy medicines cetirizine or levocetirizine (Zyrtec, Xyzal, and other trade names).
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