Cetirizine

Is cetirizine safe?

Yes, for nearly everyone at the label dose. Cetirizine (Zyrtec in the US) is a second-generation antihistamine taken once a day for hay fever, dust or pet allergies and hives. In 30 years of wide use it has built one of the cleanest safety records of any medicine on our list: overdoses usually mean a long sleep, and drug interactions are few.

It has two catches. It is more likely to make people sleepy than the other non-drowsy antihistamines, and in May 2025 the FDA added a warning about rare but severe itching after stopping long-term use. We score it 88, far above the older antihistamine diphenhydramine at 64.

What dose of cetirizine is safe?

The US label doses:

Who	Dose
Adults and children 6 and over	10 mg once a day; no more than 10 mg in 24 hours (5 mg may be enough for milder symptoms)
Adults 65 and over	Ask a doctor; children's products say 5 mg once a day, no more than 5 mg in 24 hours
Children 2 to under 6	2.5 mg once a day, up to 5 mg a day (5 mg once or 2.5 mg every 12 hours)
Children under 2	Ask a doctor
Liver or kidney disease	Ask a doctor; a lower dose may be needed

Do not take it if you have ever reacted to cetirizine or to hydroxyzine, the older drug it comes from. Levocetirizine (Xyzal) is the active half of the same molecule, so do not combine the two.

Does cetirizine make you sleepy?

Some people, yes. It crosses into the brain less than diphenhydramine but more than loratadine or fexofenadine. In the label's trials in children aged 6 to 11, drowsiness rose with dose, from 1.3% on placebo to 1.9% on 5 mg and 4.2% on 10 mg.

The label warns that drowsiness may occur, says to avoid alcohol, and asks you to take care driving or using machinery. Alcohol, sleeping pills, opioids and other sedatives add to the effect. If cetirizine makes you groggy, taking it in the evening or switching to another antihistamine are common options to discuss with a pharmacist.

Itching after you stop: the 2025 warning

In May 2025 the FDA reported 209 cases worldwide, 197 of them in the US, of pruritus (itching) after people stopped cetirizine or levocetirizine. Most had taken the drug daily for months or years; a few for about a month. The itching started a median of 2 days after the last dose, was sometimes widespread and severe enough to need treatment, and often eased when the drug was restarted. The FDA concluded that stopping the drug likely caused it, though the mechanism is unknown.

Two things follow. The risk is real but rare against the many millions of users. And it mainly concerns daily, long-term use. Anyone who has taken cetirizine every day for months and wants to stop should talk to their doctor or pharmacist about how to do it, especially if a previous attempt brought on itching. How to stop is a decision to make with a professional.

Overdose and interactions

Cetirizine has a wide margin. The prescription label describes an adult who took 150 mg, 15 times the daily dose, and was sleepy but otherwise well, and an 18-month-old who swallowed about 180 mg and became restless, then drowsy. Young children may become agitated before they get sleepy. Call Poison Help on 1-800-222-1222 in the US or NHS 111 in the UK if a child gets into the pack.

Because the liver barely processes it, cetirizine avoids most enzyme-based interactions. The label found no important effects with ketoconazole, erythromycin, azithromycin or pseudoephedrine, and only a small change with high-dose theophylline. The combinations to watch are with other sedating drugs and alcohol.

Combination products deserve a look. Zyrtec-D adds pseudoephedrine, a decongestant with its own warnings for high blood pressure, heart disease and sleep. For allergy symptoms that also include asthma, doctors sometimes add montelukast, which has very different risks.

Who should be careful

Talk to your doctor or pharmacist before taking cetirizine if you are over 65, have kidney or liver disease, are pregnant or breastfeeding (the US label does not recommend it while breastfeeding), or take sedatives, sleeping pills or opioids. Ask before giving it to a child under 2. If you need an antihistamine every day all year, it is worth asking a doctor what is driving the symptoms.

How we scored it

Overdose marginOverdose marginHow far a normal dose is from a harmful one. A wide margin means an accidental extra dose is unlikely to cause serious harm.More in the glossary (90), track record (92) and serious side effects (88) are all strong. Regulatory warnings (80) is the lowest factor, reflecting the 2025 FDA itching warning; there is no boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary or restriction. Dependence (85) accounts for the rebound itching, not any addiction risk.