Cetirizine (Zirtek allergy solution)

How does it work?

Zirtek allergy solution contains the active ingredient cetirizine, which is a type of medicine called a non-sedating antihistamine. (NB: cetirizine is also available without a brand name, ie as the generic medicine.) Cetirizine works by preventing the actions of histamine.

Histamine is a substance produced by the body as part of its defence mechanisms. It is stored in cells called mast cells, in almost all tissues of the body. When the body reacts to a foreign substance (known as an allergen, eg flower pollen), the mast cells stimulated by the allergen release their stores of histamine.

The released histamine then binds to its receptors (H1 receptors), causing a chain reaction that results in allergic symptoms. It causes an increase in blood flow to the area of the allergy, and the release of other chemicals that add to the allergic response.

All this results in the symptoms of an allergic reaction. In hayfever, histamine causes inflammation of the nose, eyes, skin or airways and results in itchy watery eyes, a runny nose, sneezing and nasal congestion.

Cetirizine works by blocking histamine H1 receptors. It does not prevent the actual release of histamine from mast cells, but prevents it binding to its receptors. This in turn prevents the release of other allergy chemicals and reduces the blood supply to the area, providing relief from the typical symptoms of hayfever.

Cetirizine can also be used to relieve the symptoms of a condition called chronic idiopathic urticaria. This is a chronic itchy rash, similar to nettle rash, but with no apparent cause. Blocking the actions of histamine relieves the itching and reduces the rash associated with this condition.

Cetirizine is called a non-sedating antihistamine as it does not enter the brain, and is therefore unlikely to cause drowsiness. However, some people may experience some slight drowsiness.

What is it used for?

  • Hayfever (seasonal allergic rhinitis) in adults and children aged two years and over.
  • Inflammation of the nasal lining due to allergies that occur thoughout the year (perennial allergic rhinitis) in adults and children aged two years and over.
  • Ongoing itchy rash with no known cause (chronic idiopathic urticaria) in adults and children aged two years and over.

How do I take it?

  • Adults and adolescents over 12 years of age should take two 5ml spoonfuls once a day.
  • Children aged from 6 to 12 years should be given one 5ml spoonful twice a day.
  • Children aged from two to six years should be given one 2.5ml spoonful (the small end of a medicine spoon) twice a day.
  • The medicine can be taken either with or without food.
  • If symptoms persist despite treatment, seek medical advice from your doctor or pharmacist.


  • Although cetirizine is a non-sedating antihistamine, occasionally some people may experience drowsiness. You should make sure you know how this medicine affects you before you perform potentially hazardous activites. If you do find this medicine makes you sleepy you should avoid drinking alcohol or taking other medicines that cause drowsiness with it, as this could make any sleepiness or reduced alertness worse.
  • If you are due to have any skin prick or patch tests to diagnose allergies you should stop taking your antihistamines at least 48 hours before the tests. This is because antihistamines can prevent or lessen the skin reactions that indicate an allergy, and so can make the test results unreliable.

Use with caution in

  • People with decreased kidney function. You may need a lower dose of this medicine if you have kidney problems. Ask your doctor or pharmacist for advice.
  • Epilepsy.

Not to be used in

  • Children under two years of age.
  • People with severe kidney failure requiring dialysis.
  • Allergy to E218, E216 or sorbitol.
  • As this medicine contains sorbitol it should not be taken by people with rare hereditary problems of fructose intolerance.

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine during pregnancy has not been established. It should not be used during pregnancy unless on the advice of a doctor. Seek medical advice from your doctor before taking this medicine if you are pregnant.
  • This medicine passes into breast milk. Although the effects of this on a nursing infant are not known, it could potentially make the baby drowsy or irritable. If you are breastfeeding you should only take this medicine on the advice of your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

  • Headache.
  • Dry mouth.
  • Dizziness.
  • Agitation.
  • Stomach or intestinal discomfort.
  • Sleepiness.
  • Fatigue.
  • Diarrhoea.
  • Pins and needles sensations.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

This medicine is not known to significantly affect other medicines. However, if you are already taking any other medicines you should always get advice from your pharmacist before taking this one as well, to make sure the combination is safe and appropriate.

Other medicines containing the same active ingredient

Benadryl allergy liquid release capsulesBenadryl allergy oral syrupBenadryl for children allergy solution
Benadryl one a day relief Boots hayfever and allergy relief Care hayfever and allergy solution
Piriteze allergy syrup Piriteze allergy tablets Zirtek allergy relief for children
Zirtek allergy relief tablets Zirtek allergy tablets

Cetirizine tablets and oral solutions are also available without a brand name, ie as the generic medicine.