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Zyrtec is a well-known antihistamine used primarily to combat allergies.

Last Modified: 28 Jun 2024

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What is Zyrtec? 

Zyrtec is a well-known antihistamine used primarily to combat allergies. It contains cetirizine hydrochloride as its active ingredient, which blocks the action of histamine in the body. Histamine produces symptoms of itching, watery eyes, runny nose, hives and sneezing. 

The drug is synthesized as cetirizine hydrochloride, a second-generation antihistamine that offers relief without causing as much less drowsiness as older antihistamines. 

Global Name

The generic name for Zyrtec is cetirizine, with Zyrtec itself being the most popular brand name. Other brand names include Aller-Tec and Zerviate.


What is Zyrtec used for? 

Zyrtec is primarily used to treat allergies, which include: 

  • Hay fever (allergic rhinitis) 
  • Dust or pet allergies 
  • Chronic urticaria (hives) 
  • Food allergies 

It can also help manage itchiness and swelling caused by acute and chronic urticaria. 

How do you use Zyrtec?  


Zyrtec is available in various forms, including tablets, chewable tablets, and syrup. 

Dosage information:

  • Adults and children 6 years and older: 10 mg once daily. 
  • Children 2 to 6 years: 5 mg once daily (syrup recommended). 
  • Infants and children under 2 years: Consult a healthcare provider


  • Children: Yes, for children 2 years and above. 
  • Adults: Yes. 
  • Elderlies: Dose adjustment may be necessary due to potential increased side effects. 
  • Pregnancy: Should be used only if clearly needed and directed by a healthcare provider. 
  • Lactation: Consult a doctor before use. 

Is there anyone who can’t take Zyrtec? 

  • Children: Not recommended for children under 2 years without doctor’s advice. 
  • Adults: Those with severe kidney impairment unless dose adjusted. 
  • Elderlies: Caution advised, especially with kidney issues. 

Allergies: Those allergic to cetirizine or hydroxyzine or any excipients of the drug should avoid Zyrtec. 

Warnings and Precautions:

  • Avoid alcohol as it can potentiate the drowsing side effects of cetirizine. 
  • Be cautious when driving or operating machinery until you know how Zyrtec affects you. 

Drug and Food/Beverage Interactions

  • Zyrtec may interact with other antihistamines, CNS depressants and alcohol. 
  • Use with caution in patients with poor kidney function. 

Side Effects

Common side effects include drowsiness, fatigue, and dry mouth. Rare, more severe reactions may include allergic reactions like hives, swelling, and breathing difficulties.

Pharmacist Tips

Storage information: 
Store at room temperature away from moisture and heat. 

Handling instructions: 
Keep the medication in its original packaging until ready to use. Follow dosage instructions carefully and adjust only under medical guidance. 


Where is Zyrtec available in Hong Kong?

Zyrtec is an over-the-counter (OTC) medication that can be sold without a prescription. It is available in all chain drug stores, including Mannings and Watsons.



Can Zyrtec be taken daily?

Yes, Zyrtec can be taken daily during allergy season or year-round for chronic conditions.

How long does Zyrtec take to start working? 

Zyrtec typically starts working within one hour of ingestion.

Can Zyrtec cause drowsiness?

Yes, although less likely than first-generation antihistamines, Zyrtec can cause drowsiness in some individuals.

Is Zyrtec safe during pregnancy?

Zyrtec should only be used in pregnancy when clearly needed, and it is best to consult with a healthcare provider.

This website provides content related to drug use and medicine for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Do not use the information on this website to diagnose or treat a health problem or disease without consulting a qualified healthcare provider. The website's owners and contributors are not liable for any repercussions, adverse effects, or consequences resulting from the use of any medication or information provided herein.

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