What to Know About Zyrtec (2025)

Common side effects of Zyrtec (cetirizine) are typically mild and can include dizziness, dry mouth, and fatigue. Less common side effects include headaches, heartburn or other stomach upset or pain, and feeling hot and/or sweating

Rare, serious side effects are possible, including irregular heartbeat, extreme weakness, and impaired urination.

People with certain health issues should not use Zyrtec.

Common Side Effects

Common side effects when taking Zyrtec include:

• Sleepiness or unusual drowsiness
• Tiredness/fatigue

The common side effects associated with Zyrtec tend to be mild and typically clear up quickly once the drug is stopped.

Let your healthcare provider know if you take any other medications that cause drowsiness (e.g., opioids, sleeping pills, muscle relaxers, or drugs that treat seizures, depression, or anxiety). Zyrtec can increase the drowsiness caused by other medications.

Less Common Side Effects

Some less commonly experienced side effects associated with Zyrtec are:

• Headache
• Dry mouth
• Sore throat
• Coughing
• Diarrhea or stomach pain (especially in children)

Rare Side Effects

Rare side effects from Zyrtec can include:

• Dizziness, feeling light-headed
• Sweating and/or feeling hot
• Nosebleeds
• Altered taste or smell
  
• Belching, indigestion, or upset stomach
• Numbness or prickling sensations
• Changes in vision
• Little or no urination
• Acute liver injury
  

Anaphylaxis is possible when taking Zyrtec.

Zyrtec Overdose Symptoms

Symptoms of a Zyrtec overdose may include:

• Extreme sleepiness
• Fast, slow, pounding, or irregular heartbeat
• Anxiety/agitation/irritability/confusion/hallucinations
• Extreme muscle weakness (trouble walking, swallowing, or speaking)
• Convulsions
  

Seek emergency medical attention or call Poison Control at 1-800-222-1222 if you experience these symptoms while taking Zyrtec.

Who Should Not Take Zyrtec

Zyrtec is generally considered safe, but some people should not take the drugs due to the potential harm. Do not take Zyrtec if you:

• Are allergic to cetirizine
• Have glaucoma (increased eye pressure)
• Have advanced liver disease, including cirrhosis
• Have renal disease or kidney failure
• Have an enlarged prostate and are unable to empty your bladder completely

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.

Dosage and Directions

Zyrtec is available over-the-counter (OTC) as a tablet, chewable tablet, and syrup. Each dose is measured in milligrams (mg). There are recommended dosages for specific age groups.

Recommended dose for adults and children ages 6 to 64:

• 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)

Recommended dose for children ages 2 to 5 and adults 65 and over:

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

Zyrtec is one of the safest antihistamines to use in adults 65 and over. However, the recommended dose of Zyrtec for those in this age group is lower than for younger adults. This is because all second-generation antihistamines are more likely to cause side effects (like sleepiness, anxiety, and tremors) in older people.

For children under 2:

• One half (2.5 mg) to one (5 mg) teaspoon of syrup every 24 hours (maximum 5 mg per day). However, consult your pediatrician before treating children under 2 with Zyrtec.

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

Alternatives to Zyrtec

If you cannot use Zyrtec, you can try another second-generation antihistamine like Allegra (fexofenadine) or Claritin (loratadine). However, these OTC drugs have similar mechanisms of action to Zyrtec—and similar potential side effects. So, they may not be an option if you cannot tolerate the side effects of Zyrtec.

Some non-drug alternatives may prove beneficial during seasonal allergies, including:

• Avoiding allergy triggers: If tree pollens or grasses like ragweed cause hay fever, keep track of pollen counts locally and avoid going outdoors when 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 has been clinically shown to help clear nasal passages.

Summary

Zyrtec is a second-generation antihistamine used to relieve symptoms of seasonal allergies such as sneezing, runny nose, and itchy eyes. It is available OTC for use in adults and children.

Side effects can include drowsiness, dry mouth, sore throat, dizziness, and stomach pain. Serious side effects can include rapid or irregular heartbeat, mood changes such as anxiety, and problems urinating.

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 an allergist (allergy specialist).