The standard adult dose of cetirizine is 10 mg once per day. That single daily tablet is the recommended maximum for over-the-counter use in adults and children 12 and older, and most people get full allergy relief at that dose. Some adults start at 5 mg if their symptoms are mild, but 10 mg is where most clinical trials have landed as the effective amount.
Standard Doses by Age
Cetirizine is taken once a day, with or without food, and you can take it at whatever time works best for your schedule. For adults and children 12 and older, the FDA-approved dose is 5 to 10 mg daily depending on symptom severity. A 5 mg dose may be enough for mild seasonal sniffles, while 10 mg is the standard choice for moderate to severe allergies or hives.
For children under 12, doses are lower. Children aged 6 to 11 typically take 5 to 10 mg once daily. Children aged 2 to 5 usually take 2.5 mg once daily, which can be increased to 5 mg (either as a single dose or split into two 2.5 mg doses). For children between 6 months and 2 years, the usual dose is 2.5 mg once daily. Liquid formulations make it easier to measure these smaller amounts precisely.
When Doctors Prescribe Higher Doses
There is one major exception to the 10 mg ceiling: chronic hives (chronic urticaria). When standard doses don’t control persistent hives, doctors sometimes increase cetirizine to up to four times the normal daily dose. That means up to 40 mg per day for adults and children 6 and older. This is not something you should do on your own. These higher doses are prescribed under medical supervision, typically after a standard dose has failed and a doctor has confirmed the diagnosis. International allergy guidelines support this stepwise approach before moving to more specialized treatments.
Outside of that specific situation, there is no established benefit to taking more than 10 mg daily for hay fever or other common allergies. Doubling up because your allergies feel worse one day won’t meaningfully improve relief, but it will increase your chances of side effects like drowsiness.
What Happens if You Take Too Much
Cetirizine has a relatively wide safety margin compared to older antihistamines, but overdose is still possible and unpleasant. Symptoms of taking too much include agitation, rapid heart rate, dilated pupils, and excessive drowsiness. In more serious cases, particularly large overdoses, people have experienced hallucinations, fever, flushed and dry skin, blurred vision, and difficulty urinating. These symptoms resemble what’s called anticholinergic toxicity, where the body’s normal involuntary functions (sweating, digestion, pupil control) get disrupted.
If you accidentally take a double dose, you’re unlikely to experience anything beyond extra sleepiness. But if a child gets into a bottle or someone takes significantly more than directed, contact Poison Control (1-800-222-1222 in the U.S.) right away.
Alcohol and Other Sedatives
Cetirizine causes less drowsiness than older antihistamines like diphenhydramine, but it still affects alertness in some people. Combining it with alcohol amplifies that effect. Alcohol increases the drowsiness, dizziness, and impaired coordination that cetirizine can cause on its own. Since cetirizine stays active in your bloodstream for up to 24 hours, this interaction isn’t limited to the hour you take your pill. Drinking at any point during the day you’ve taken cetirizine carries some risk of added impairment.
The same logic applies to other sedating substances. Taking cetirizine alongside benzodiazepines (prescribed for anxiety or sleep) or opioid pain medications can cause excessive drowsiness. If you take any of these regularly, that’s worth flagging with your pharmacist before adding daily cetirizine.
Who Should Take a Lower Dose
Cetirizine is processed through the kidneys, so people with reduced kidney function clear the drug more slowly. If you have kidney disease, a lower dose or less frequent dosing may be appropriate. The same applies to people with significant liver problems, since the liver plays a supporting role in breaking down the drug. Older adults often have naturally declining kidney function and tend to be more sensitive to the sedating effects, so starting at 5 mg is a reasonable approach.
Withdrawal Itching After Long-Term Use
In May 2025, the FDA added a new warning to cetirizine labeling: stopping the medication after long-term daily use can trigger intense, widespread itching. This rebound itching is rare but can be severe enough that people mistake it for a new allergic condition and restart the medication, creating a cycle that’s hard to break. If you’ve been taking cetirizine daily for months or years and want to stop, tapering gradually rather than quitting abruptly may help reduce this effect.