Cetirizine is a once-daily non-sedating antihistamine, usually 10 mg. It treats hay fever, allergic rhinitis, itchy watery eyes, hives and allergic itching. It causes far less drowsiness than older antihistamines and is one of the most effective options for itching.
What is Cetirizine?
Cetirizine is a second-generation antihistamine, dispensed as 10 mg tablets and as a syrup for children. In South Africa it is sold under its own name and as Austell Cetirizine, Seasoneze, Allecet, Zelary, Zyrtec and Texa.
When the immune system treats something harmless as a threat — pollen, dust mite, mould, animal dander — mast cells release histamine. Histamine binding to H1 receptors produces the familiar cluster: sneezing, a runny itchy nose, watery eyes, and in the skin, weals and itching. Cetirizine occupies those receptors so histamine cannot bind.
The generation matters. Older antihistamines such as the chlorphenamine in Allergex cross readily into the brain, where the same receptors govern wakefulness, and cause pronounced drowsiness. Cetirizine was designed to cross far less — which is what makes a once-daily antihistamine practical for someone who has to drive, work or study.
Within that group, cetirizine occupies a useful position. It is among the most effective for itching and for hives, though it sedates slightly more than loratadine or fexofenadine. For most people that trade favours cetirizine.
So many brands contain it that accidental doubling is a real risk. Check the active ingredient before combining any allergy or cold product.
What is Cetirizine commonly used for?
- Hay fever (seasonal allergic rhinitis) — sneezing, runny and itchy nose, itchy throat, watery eyes.
- Perennial allergic rhinitis, from dust mite, mould or pet dander.
- Allergic conjunctivitis — itchy, red, watery eyes.
- Chronic urticaria (hives), where it is a first-line treatment.
- Itching from allergic skin conditions, eczema flares and insect bites.
- Mild allergic reactions.
For hives, cetirizine deserves particular mention. Chronic urticaria is often treated with a second-generation antihistamine at higher than the standard once-daily amount — sometimes considerably higher — under medical supervision, and this works well for many people. Do not increase it yourself, but if standard treatment is not controlling hives, it is worth asking a doctor about, because many people give up assuming nothing more can be done.
For seasonal allergy, timing improves results. An antihistamine blocks histamine from binding but does not reverse a reaction already under way. Starting it a week or two before your usual trigger season, and taking it daily through it rather than only on bad days, gives noticeably better control.
Two things it does not do: it does not treat a cold, which is viral rather than histamine-driven, and it does not treat asthma or substitute for an inhaler.
For blocked nose, antihistamines underperform. Congestion in allergic rhinitis is driven more by inflammation than histamine, and a steroid nasal spray works considerably better.
How Cetirizine fits into this medicine category
| Group | Examples | Note |
|---|---|---|
| Second-generation antihistamines | Cetirizine, loratadine, fexofenadine | Once daily; little drowsiness |
| First-generation antihistamines | Chlorphenamine (Allergex, Rhineton), cyproheptadine | Effective; markedly sedating |
| Steroid nasal sprays | Fluticasone, mometasone | Best for congestion; work over days |
| Decongestants | Pseudoephedrine, oxymetazoline | Short-term only; rebound with overuse |
| Eye drops | Sodium cromoglycate, antihistamine drops | Targeted relief for itchy eyes |
See the allergy, cold and flu medicines hub.
What to check before using Cetirizine
Take one tablet once daily, at any time, with or without food.
Do not take it with another antihistamine — check the active ingredients on any allergy, cold or flu product, since cetirizine appears under many brand names.
Speak to a pharmacist or doctor if:
- You have kidney disease. Cetirizine is cleared largely by the kidneys, and a reduced amount is often appropriate.
- You have liver disease.
- You are pregnant or breastfeeding.
- You are older, where drowsiness and urinary difficulty are more likely.
- You have an enlarged prostate or difficulty passing urine.
- You have epilepsy.
- The medicine is for a child. Syrups and lower strengths exist — check the right form and amount.
- You are due allergy testing. Antihistamines suppress skin prick test results and usually must be stopped several days beforehand — tell whoever arranges the test.
Avoid alcohol until you know how it affects you.
Follow the pack instructions. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
A minority do feel drowsy. If you are one of them, take it in the evening, or ask a pharmacist about loratadine or fexofenadine, which sedate less. Do not drive until you know how you respond.
Dry mouth, headache and tiredness are the other common effects, usually mild.
Do not stop suddenly after long continuous use. A withdrawal itch — intense generalised itching lasting days to weeks after stopping — is recognised in people who have taken cetirizine daily for months or years. It is uncommon and it resolves, but it catches people out badly because it looks like the allergy returning far worse. If you have been on it a long time, taper rather than stopping outright.
If it is not helping, something else is going on. Persistent symptoms despite a daily antihistamine may mean congestion is the dominant problem, that the trigger is not allergic, or that additional treatment is needed. Symptoms beyond a few weeks warrant proper assessment.
Reducing exposure helps and lowers how much medicine you need: dust mite covers on mattress and pillows, windows shut at high pollen times, showering and changing after being outdoors, drying laundry indoors in pollen season, and keeping pets out of bedrooms.
Seek urgent medical attention for swelling of the face, lips, tongue or throat, difficulty breathing or swallowing, wheezing, faintness with a widespread rash, or a rash that blisters or peels. Hives with any swelling of the mouth or throat is an emergency, not an allergy inconvenience.
Related medicine guides
Frequently asked questions
What is cetirizine 10 mg used for? Hay fever and allergic rhinitis, itchy watery eyes, hives and allergic itching.
Will it make me drowsy? Far less than older antihistamines, though a minority of people notice it. Take it in the evening if so.
How is it different from loratadine? Both are once-daily and non-sedating. Cetirizine is somewhat more effective for itching and hives; loratadine sedates even less.
Can I take it for a cold? It will not treat a cold, which is viral rather than histamine-driven. It may slightly dry a runny nose.
Will it clear a blocked nose? Only partly. Congestion responds better to a steroid nasal spray used consistently.
Can I take more than one a day for hives? Not on your own. Higher amounts are used for chronic hives, but only under medical supervision — ask your doctor rather than increasing it yourself.