Zyrtec Side Effects and Drug Warnings

Zyrtec (cetirizine) is an over-the-counter (OTC) antihistamine medication that relieves symptoms of seasonal allergy, including itching, sneezing, and a runny nose.

Common side effects of Zyrtec are typically mild and may include:

  • Drowsiness
  • Fatigue
  • Dizziness
  • Dry mouth
  • Sore throat
  • Cough
  • Stomach pain
  • Nausea
  • Constipation
  • Headaches

This article explains how Zyrtec works and how it is dosed in adults and children. It also looks at common and severe side effects, as well as when Zyrtec should not be used for safety reasons.

A woman with allergies blowing her nose
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How Zyrtec Works

The active ingredient of Zyrtec is called cetirizine. It is a second-generation antihistamine that works by blocking the action of a chemical called histamine. Histamine is the chemical produced by the immune system that triggers allergy symptoms.

By doing so, Zyrtec can help relieve the following seasonal allergy symptoms:

  • Runny nose
  • Sneezing
  • Postnasal drip
  • Itchy eyes, nose, or throat
  • Hives

Unlike first-generation antihistamines such as Benadryl (diphenhydramine), Zyrtec does not cross the blood-brain barrier that separates the brain from the rest of the body. Because of this, second-generation antihistamines like Zyrtec are less likely to cause drowsiness than their earlier-generation cousins.

Common Zyrtec Side Effects

Zyrtec can cause side effects affecting the digestive tract, nervous system, respiratory tract, and others. Side effects tend to be mild and almost invariably clear once the drug is stopped.

Organ System Zyrtec Side Effects
Nervous system •Drowsiness
•Altered taste or smell
•Burning, numbness, or prickly sensations
•Nervousness or anxiety
Digestive tract •Dry mouth
•Stomach pain
•Upset stomach
•Nausea, vomiting
•Flatulence (gas)
Respiratory tract •Sore throat
•Stuffy nose
Eyes •Blurred vision
•Eye pain
Skin, muscles, and bone •Increased sweating
•Muscle aches and/or weakness
•Joint pain
Heart and cardiovascular system •Flushing
•Hot flashes
•Heart palpitation
•High blood pressure
Urinary tract •Reduced urination
•Pain with urination

Severe Side Effects

Certain Zyrtec side effects can be serious. If you experience any of the following after taking Zyrtec, call your doctor immediately:

  • Rapid or irregular heartbeats
  • Hyperactivity
  • Severe restlessness
  • Extreme weakness
  • Tremors (uncontrollable shaking)
  • Confusion
  • Change in vision
  • Little or no urination

When to Call 911

On rare occasions, Zyrtec can cause a potentially life-threatening, whole-body allergy known as anaphylaxis. Call 911 or rush to your nearest emergency room if you experience any of the following after taking Zyrtec:

  • Shortness of breath
  • Wheezing
  • Sudden rash or hives
  • Nausea and vomiting
  • Rapid or slowed heartbeats
  • Dizziness, lightheadedness, or fainting
  • Swelling of the face, mouth, or throat
  • A feeling of impending doom

Dosage and Directions

Zyrtec is available over the counter as a tablet, chewable tablet, and syrup. Each dose is measured in milligrams (mg).

The recommended dose for adults and children ages 6 to 64 is:

  • One 10-mg tablet every 24 hours (maximum 10 mg per day)
  • One to two 5-mg chewable tablets every 24 hours (maximum 10 mg per day)

The recommended dose for children ages 2 to 6 and adults 65 and over is:

  • One half (2.5 mg) to one (5 mg) teaspoon of syrup every 24 hours (maximum 5 mg per day)

Zyrtec is actually of the safest antihistamine to use in adults 65 and over. That said, the recommended dose of Zyrtec for people in this age group is lower than for other adults due to the fact that all second-generation antihistamines are more likely to cause side effects in older people. These include sleepiness, anxiety, and tremors.

For children under 2:

  • Zyrtec should only be used under the direction of a pediatrician.

Zyrtec is taken with or without food. Measure the syrup using the dosing syringe provided and not a kitchen spoon. Chewable tablets should be chewed and not swallowed whole.

Can Taking Zyrtec Daily Be Harmful?

Zyrtec is safe to take daily and is generally regarded as safe for long-term use. There is a very small risk of liver toxicity with long-term use. While this is considered rare, anyone who uses Zyrtec on an ongoing basis should have their liver enzymes tested just in case.

Who Should Not Take Zyrtec

Zyrtec is generally considered safe, but there are some people who should not take the drugs due to the potential harm.

Do not take Zyrtec if you:

Speak with your healthcare provider before using Zyrtec if you are pregnant, trying to become pregnant, or breastfeeding.

Zyrtec should not be taken with alcohol or marijuana. Doing so can increase the risk of drowsiness and can make driving or handling heavy equipment hazardous.

Alternatives to Zyrtec

If you cannot use Zyrtec for whatever reason, you can try other second-generation antihistamines like Allegra (fexofenadine) or Claritin (fexofenadine).

With that said, these over-the-counter drugs have similar mechanisms of action and side effects as Zyrtec, so they may not be an option if you cannot tolerate the side effects of Zyrtec.

There are some natural alternatives that may help if you suffer from seasonal allergies:

  • Avoidance of allergy triggers: If tree pollens or grasses like ragweed cause hay fever, keep track of pollen counts on the local news and avoid going outdoors if pollen counts are high.
  • Nasal irrigation: Clearing the sinuses with a saline solution and neti pot can help reduce stuffiness, sneezing, and postnatal drip.
  • Steam inhalation: Inhaling steam can also help clear nasal passages, particularly when menthol or camphor is added.


Zyrtec (cetirizine) is a second-generation antihistamine used to relieve symptoms of seasonal allergies such as sneezing, runny nose, and itchy eyes. It is available over the counter for use in adults and children 2 years and over.

Side effects include drowsiness, dry mouth, sore throat, dizziness, and stomach pain.

A Word From Verywell

Zyrtec is an effective option for treating seasonal allergies and other allergic conditions. However, if your allergy symptoms are severe and Zyrtec fails to provide relief, ask your healthcare providers for a referral to a specialist known as an allergist.

An allergist can conduct tests to pinpoint which allergens (allergy-causing substances) you are sensitive to. Based on the findings, they may be able to offer allergy shots to gradually desensitize you to common allergens such as pollen.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Food and Drug Administration. Zyrtec (cetirizine hydrochloride) tablets and syrup for oral use.

  2. Bozek A. Pharmacological management of allergic rhinitis in the elderly. Drugs Aging. 2017;34(1):21–8. doi:10.1007/s40266-016-0425-7

  3. Urdaneta ER, Patel MK, Franklin KB, Tian X, Wu MM. Assessment of different cetirizine dosing strategies on seasonal allergic rhinitis symptoms: findings of two randomized trials. Allergy Rhinol (Providence). 2018 Jan-Dec;9:2152656718783630. doi:10.1177/2152656718783630

  4. Corsico AG, Leonardi S, Licari A, et al. Focus on the cetirizine use in clinical practice: a reappraisal 30 years later. Multidiscip Respir Med. 2019;14:40. doi:10.1186/s40248-019-0203-6

Additional Reading

By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.