Sounds like 'seh-TEER-ah-zeen'

Cetirizine is an antihistamine used to treat and prevent allergies such as hay fever. Find out how to take it safely and possible side effects.

Type of medicine Also called
  • Belongs to a group of medicines known as antihistamines (allergy treatment)
  • Non-sedating antihistamine
  • Zista®
  • Histaclear®
  • Allerid C®
  • Cetirizine-AFT® 
  • Zyrtec®
  • Razene®
  • Zetop®

What is cetirizine?

Cetirizine is used to treat and prevent allergies such as hay fever (sneezing, runny or itchy nose, itchy eyes) or skin allergies such as hives (itching, redness, lumps). It works by blocking a chemical in your body, called histamine, which is released during an allergic reaction. 

Cetirizine belongs to a group of medicines known as antihistamines. Cetirizine is a non-sedating antihistamine, which means that it is less likely to cause drowsiness or make you feel sleepy. In New Zealand, cetirizine is available as tablets or as a liquid. Read more about antihistamines.


  • The usual dose of cetirizine for adults and children over 12 years, is 1 tablet (10 milligrams) once a day.
  • The dose for children under 12 years will depend on their age and weight. Your doctor or pharmacist will advise you on the correct dose for your child.
  • You can just take cetirizine on the days you need it. It can be restarted if the symptoms come back. 
  • Some people take cetirizine for a few weeks when their allergies are a problem, such as in springtime. Others take it long-term to help control allergy symptoms. 

How to take cetirizine

  • Timing: Take cetirizine once a day at the same time each day. You can take cetirizine with or without food. Swallow the tablet whole, with a glass of water.
  • Limit drinking alcohol while you are taking cetirizine. It may increase your chance of side effects such as sleepiness.  
  • Missed dose: It is not harmful if you miss your cetirizine dose. If you forget to take your dose, and you usually take it regularly, take it as soon as you remember that day. If it is less than 12 hours for your next dose, just take the next dose at the right time. Do not take double the dose.

Precautions before starting cetirizine

  • Are you are pregnant, trying for a baby or breastfeeding?
  • Do you have epilepsy?
  • Do you have any problems with the way your kidneys work?
  • Are you taking or using any other medicines? This includes any medicines that you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start cetirizine. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of cetirizine?

Like all medicines, cetirizine can cause side effects, although not everyone gets them. Often side effects improve as your body adjusts to the new medicine.

Side effects What should I do?
  • Tiredness
  • Sleepiness
  • Try taking cetirizine at night.
  • Be careful when driving or using tools until you know how this medicine affects you.
  • Limit drinking alcohol – it makes these symptoms worse.
  • Changes in eyesight
  • Dry mouth
  • Blurred vision
  • Feeling dizzy or confused
  • Problems passing urine
  • Constipation
  • Headache
  • Tell your doctor.
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product


Cetirizine may interact with some medicines so check with your pharmacist before starting cetirizine or before starting any new medicines. If taken with other antihistamines (such as some cough and cold medication) it may cause added sleepiness.

Learn more

Razene Medsafe, NZ
Cetirizine New Zealand Formulary


  1. Cetirizine hydrochloride New Zealand Formulary
  2. Antihistamines New Zealand Formulary

Additional resources for healthcare professionals

Razene Medsafe, NZ‎
Zyrtec Medsafe, NZ‎
Diagnosis and treatment of urticaria BPAC, NZ, 2012

Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 31 Jul 2020