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Cetirizine: uses, dosage and side effects

Cetirizine is a second-generation antihistamine used for hay fever, other allergic rhinitis and itchy skin conditions such as urticaria. In Ireland it is sold in pharmacies without a prescription, so no consultation and no prescription document are needed to buy it. This page explains what cetirizine does, how it is taken, which side effects are reported and when an allergy problem is no longer something to manage from the pharmacy shelf. It is information only, and we are not offering you a consultation for a medicine you can simply buy.

What cetirizine is used for

Cetirizine relieves the symptoms of allergy: sneezing, a runny or itchy nose, itchy and watery eyes, and the itching and weals of urticaria. It is used for seasonal allergic rhinitis, which most people call hay fever, for year-round allergic rhinitis caused by house dust mite, pets or mould, and for chronic idiopathic urticaria. It blocks histamine at H1 receptors, so it stops the reaction that histamine causes rather than removing the allergen or curing the allergy. It is called second generation because it crosses into the brain far less than older antihistamines and therefore causes much less drowsiness, though it is not entirely free of it. Cetirizine does not treat asthma and it is not a treatment for anaphylaxis: a severe allergic reaction needs adrenaline and emergency care, not an antihistamine tablet. For a blocked nose alone, a steroid nasal spray often works better.

Side effects of cetirizine

Cetirizine is well tolerated by most people. The effects reported most often are drowsiness or sleepiness, dry mouth, headache, tiredness, dizziness and, in some people, a mild sore throat or abdominal discomfort. Drowsiness is much less common than with older antihistamines such as chlorphenamine, but it is real for a minority, which is why the packaging tells you to see how the tablets affect you before driving or using machinery. Less commonly people report agitation, especially in children, or difficulty passing urine. Serious reactions are rare and include severe allergic reaction to the tablet itself. Some people who take cetirizine daily for a long period report intense itching for days or weeks after stopping; if that happens, tell a pharmacist rather than assuming your allergy has worsened. Seek urgent medical help immediately for swelling of the lips, tongue or throat with breathing difficulty; in an emergency in Ireland ring 112 or 999.

Dosage and how to take it

Cetirizine is usually taken once a day, as a tablet swallowed with water or as an oral solution for children and for adults who cannot swallow tablets, and it can be taken with or without food. The dose for adults, and separate lower doses for children by age, are printed on the pack and in the leaflet; because it is a pharmacy medicine, the pharmacist can confirm the right one for you or your child and check that nothing else you take conflicts. Reduced kidney function usually means a lower dose or longer intervals, which is one of the few reasons to ask before buying. Taking it in the evening suits people who notice any drowsiness. For seasonal hay fever it works better taken regularly through the season rather than only on bad days, because the aim is to keep histamine blocked continuously. Do not exceed the stated dose.

Is cetirizine available without a prescription in Ireland?

Yes. Cetirizine is sold from pharmacies in Ireland without a prescription, in tablets and as an oral solution, under several brand names and as unbranded generics. That means no doctor, no prescription document and no consultation fee are needed to obtain it: you ask at the counter and the pharmacist supplies it. Because it is a pharmacy medicine, the pharmacist may ask who it is for, what other medicines you take and whether you have kidney problems, which is a safety check rather than an obstacle. We do not sell consultations for medicines you can buy over the counter, and we would not issue a prescription for cetirizine, because paying for one adds cost and gains you nothing. If your symptoms are not controlled by an over-the-counter antihistamine, the useful next step is a GP or a pharmacist review, not a prescription for the same medicine.

When allergy symptoms need a doctor rather than a pharmacy

Most hay fever is managed perfectly well from the pharmacy shelf, but some situations need assessment. See a GP if symptoms persist despite a regular antihistamine plus a steroid nasal spray, if you have wheeze, chest tightness, cough or breathlessness that could be asthma, if a child has poor sleep or is missing school because of symptoms, if you have unilateral nasal blockage, bleeding or loss of smell that does not fit an allergy pattern, or if urticaria lasts more than six weeks. A history of a severe reaction to food, insect stings or medicines needs a proper allergy assessment and possibly an adrenaline auto-injector, which is well beyond what any antihistamine can do. Seek emergency care immediately for swelling of the tongue or throat, difficulty breathing or swallowing, or faintness with a rash: that is anaphylaxis, and in Ireland the number to ring is 112 or 999.

Cost and reimbursement in Ireland

Bought over the counter, cetirizine is inexpensive, and generic packs are usually a fraction of the price of the best-known brands even though the active substance and strength are the same. Prices differ between pharmacies, and larger packs are generally better value for a whole hay fever season. Because you are buying it without a prescription, over-the-counter purchases are not covered by the Drugs Payment Scheme, which applies to prescribed medicines dispensed in a community pharmacy. If a GP prescribes an antihistamine for you, for example as part of treating chronic urticaria, then the usual arrangements apply: the GMS scheme for medical card holders with a charge per item, or the Drugs Payment Scheme for everyone else, with the current charge and monthly cap published by the HSE. Ask the pharmacist which route is cheaper for your situation before assuming a prescription saves money.

Interactions and alcohol

Cetirizine has few significant interactions, which is one reason it is available without a prescription. The interaction that matters most is with anything else that causes drowsiness: alcohol, sedating older antihistamines, sleep medicines, strong painkillers and some antidepressants. Alcohol is not formally forbidden with cetirizine, but the combination increases the chance of feeling drowsy or slowed, and that affects driving. Combination cold and flu products often already contain an antihistamine, so check the label before adding cetirizine on top of one, and the same applies to some over-the-counter sleep aids. Theophylline used in respiratory disease can affect cetirizine levels. If you have reduced kidney function or take several regular medicines, ask the pharmacist to check before you start. Tell the pharmacist about everything you take, including herbal products, because being on sale without a prescription does not mean nothing can interact.

Who should not take cetirizine

Cetirizine should not be taken by anyone allergic to it, to hydroxyzine or to piperazine derivatives, or to any ingredient of the particular product, and it is contraindicated in severe kidney impairment at the usual dose. People with reduced kidney function generally need a lower dose or a longer interval between doses. Caution applies in epilepsy or a tendency to seizures, in difficulty passing urine because of prostate enlargement or spinal cord problems, and in older adults, who are more sensitive to any sedating effect. Some oral solutions and tablets contain excipients such as lactose or sorbitol that matter to a minority. Children need the dose for their age, not a fraction of an adult tablet guessed at home. Antihistamines can suppress skin reactions, so if you are having allergy skin testing, tell the clinic, because the medicine usually has to be stopped for a period beforehand.

Generic and brand names

The active substance is cetirizine hydrochloride, and in Ireland it is sold both under familiar brand names and as generic pharmacy own-label packs. The active substance and the strength are the same, so the choice is about price, pack size and formulation rather than effectiveness. Levocetirizine is a closely related medicine, the active half of the same molecule, sold separately; it is not the same product and doses are not interchangeable. Loratadine and fexofenadine are alternative non-sedating antihistamines, and people who respond poorly to one sometimes do better on another, which is a reasonable thing to try with pharmacist advice. Combination products pair an antihistamine with a decongestant, and those are not suitable for everyone, particularly people with high blood pressure. Check the active substance on the box rather than the brand, because buying two products that both contain cetirizine is an easy way to double a dose by accident.

Pregnancy and breastfeeding

Cetirizine is one of the antihistamines with more reassuring experience of use in pregnancy, but that does not make it automatic: pharmacy sale rules still direct pregnant and breastfeeding women to ask a pharmacist or doctor before using it, and that advice is worth following rather than treating the shelf as permission. Non-medicine measures come first in pregnancy, including saline nasal rinses, avoiding the trigger where possible and, for nasal symptoms, treatments a GP can recommend. Cetirizine passes into breast milk in small amounts, and a sedating effect on the infant is theoretically possible, so a pharmacist may suggest an alternative or the lowest effective dose. If allergy symptoms are severe enough to disturb sleep during pregnancy, that is a reason to see a GP rather than to self-treat with increasing doses. Never exceed the stated dose while pregnant or breastfeeding.

Patient information leaflet

Every pack sold in Ireland contains a patient information leaflet, and the same leaflet is published online. The Health Products Regulatory Authority (HPRA) is the medicines regulator here and lists authorised products together with their leaflets and summaries of product characteristics; medicines.ie publishes the same documents for products marketed in Ireland. With an over-the-counter medicine the leaflet is easy to throw away with the box, so keep it, particularly if the pack is for a child and the dose depends on age. Read it before giving a first dose and check the active substance against anything else you are taking. If anything does not match what you were told, ask your pharmacist rather than guessing; pharmacists in Ireland are registered with the Pharmaceutical Society of Ireland. A suspected side effect can be reported by you directly to the HPRA, and that applies to medicines bought without a prescription too.

Who wrote and checked this page

This page was prepared by the medical content team at MEDINOW Sp. z o.o. and reviewed by lek. Damian Wojno, a doctor registered in Poland, PWZ no. 3211301. He holds no Irish registration and does not practise in Ireland; he works to Polish professional rules and issues cross-border prescriptions under Directive 2011/24/EU and Directive 2012/52/EU, which is the framework an Irish pharmacist applies when a prescription comes from another EU or EEA country. The content was verified on 29 August 2026 against the sources listed below, all of them official or regulator-published. This page is general information about a medicine: it is not personal medical advice, not a diagnosis and not an offer of the medicine itself, which we never supply. If your symptoms are new, severe or changing, contact your GP or a pharmacist; in an emergency in Ireland ring 112 or 999.

Is cetirizine prescription-only in Ireland?

No. Cetirizine is sold in Irish pharmacies without a prescription, as tablets and as an oral solution. You do not need a consultation to buy it, and paying for a prescription for it would add cost without adding anything useful.

How long does it take to work?

Most people notice relief within about an hour of the first dose, and the effect lasts through the day, which is why it is taken once daily. For seasonal hay fever it works best taken regularly through the season rather than only on the worst days.

What are the common side effects?

Drowsiness in a minority of people, dry mouth, headache, tiredness and dizziness are the most frequently reported. See how it affects you before driving, and remember that combining it with alcohol or other sedating medicines increases that effect.

Can I drink alcohol with it?

There is no formal ban, but alcohol and cetirizine can both cause drowsiness and the combination adds to it. If you notice any sedation on the tablets, keep alcohol to a minimum and do not drive.

Do I need a prescription or a consultation for cetirizine?

No, and we do not sell one for it. If an over-the-counter antihistamine plus a steroid nasal spray is not controlling your symptoms, or if there is wheeze, breathlessness or a rash lasting more than six weeks, see a GP for assessment instead of buying more of the same medicine.