Sounds like 'seh-TEER-ah-zeen'

Easy-to-read medicine information about cetirizine – what is it, how to take cetirizine safely and possible side effects.

Type of medicineAlso called
  • Belongs to a group of medicines known as antihistamines (allergy treatment)
  • Non-sedating antihistamine
  • Histaclear®
  • Allerid C®
  • 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 allergies of the skin (itching, redness, lumps on the skin called hives).
  • It works by blocking a chemical in the body, called histamine, which is released during an allergic reaction.
  • Cetirizine belongs to a group of medicines known as antihistamines. More specifically, cetirizine is a non-sedating antihistamine, which means that it is less likely to cause drowsiness, or make you feel sleepy.  


  • The usual dose of cetirizine is 1 tablet (10 milligrams) once a day.
  • 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

  • Take cetirizine once a day at the same time each day, either in the morning OR in the evening.
  • 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.  
  • It is not harmful if you miss your cetirizine dose. If you forget to take your dose, 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.

Possible side effects

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

Side effectsWhat 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
  • Changes in eyesight
  • Dry mouth
  • Problems passing urine
  • Constipation
  • Headache
  • Tell your doctor 


  • Cetirizine may interact with some medicines that are available  without a prescription, so check with your pharmacist.
  • If taken with other antihistamines (such as some cough and cold medication)  it may cause added sleepiness.

Learn More

Medsafe Consumer Information Sheet: 

New Zealand Formulary Patient Information: Cetirizine

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft. Health Navigator NZ Last reviewed: 20 Nov 2015