Cetirizine 10mg tablets are an antihistamine used to relieve symptoms of hay fever, seasonal allergies, and hives. A single tablet works within 20 to 60 minutes and provides relief for a full 24 hours, making it a once-daily option for managing allergic symptoms.
Allergy Symptoms It Treats
The standard 10mg dose is designed for adults and children 12 and older to temporarily relieve the most common upper respiratory allergy symptoms: runny nose, sneezing, itchy or watery eyes, and itching of the nose or throat. These symptoms can stem from seasonal triggers like pollen or year-round allergens such as dust mites, pet dander, and mold.
Cetirizine works by stabilizing the histamine receptors on your cells so they stop reacting to allergens. When your immune system detects pollen or another trigger, it releases histamine, which is the chemical responsible for that familiar cascade of sneezing, itching, and congestion. Cetirizine essentially locks histamine out of its receptors, preventing the chain reaction before symptoms spiral.
Treating Hives
Beyond seasonal allergies, cetirizine is widely used for chronic hives (also called chronic urticaria), a condition where itchy, raised welts appear on the skin repeatedly over weeks or months, sometimes without a clear trigger. Antihistamines in cetirizine’s class are effective for roughly 50% of people with chronic hives. For the other half, a doctor may increase the dose or add other treatments.
If you’re dealing with a one-time allergic skin reaction, such as hives from a food or insect sting, cetirizine can help reduce the itching and swelling while the reaction runs its course.
How Quickly It Works and How Long It Lasts
Most people notice symptom relief within 20 to 60 minutes of taking a 10mg tablet. The effects typically last about 24 hours, which is why the standard recommendation is one tablet per day. Taking it at the same time each day helps maintain steady relief, and many people with seasonal allergies find that taking it in the evening minimizes any daytime drowsiness.
Drowsiness and Side Effects
Cetirizine is classified as a second-generation antihistamine, meaning it causes significantly less drowsiness than older options like diphenhydramine (Benadryl). That said, it’s not completely free of sedating effects. In clinical trials, 14% of people taking 10mg reported some sleepiness, compared to 6% on a placebo. That’s a real but modest difference, and only about 1% of people found it bothersome enough to stop taking the medication.
The drowsiness tends to be most noticeable during the first few days of use and often fades as your body adjusts. If you’re sensitive to this effect, starting with a 5mg dose (half a tablet) can help you gauge your response before moving to the full 10mg.
Alcohol and Other Sedating Substances
Cetirizine stays in your bloodstream for up to 24 hours, and during that window, alcohol can amplify its sedating effects. The combination can impair coordination and judgment beyond what either substance would cause alone. For the same reason, cetirizine should not be taken alongside other sedating medications such as benzodiazepines or opioids, as the combined drowsiness can become excessive.
Dosing for Children
Children aged 6 to 11 can take 5 to 10mg once daily, while those 12 and older follow the standard adult dose of 10mg once daily. For younger children in the 6 to 11 range, starting at 5mg is common, since cetirizine tends to be slightly more sedating in kids than some alternatives like loratadine or fexofenadine. Only one antihistamine should be used at a time.
Kidney and Liver Considerations
Your kidneys handle most of the work clearing cetirizine from your body. If you have reduced kidney function or liver disease, the drug clears more slowly, which means a standard dose can build up and cause stronger side effects, particularly drowsiness. In these situations, a lower dose of 5mg once daily is typically recommended. The same applies to children aged 6 to 11 with kidney or liver impairment.
Use During Pregnancy and Breastfeeding
Cetirizine is considered one of the safer antihistamine choices during pregnancy. While large-scale studies are limited, there is no evidence suggesting it harms the baby. For breastfeeding, it’s one of the preferred options because only very small amounts pass into breast milk. It has been widely used by breastfeeding parents for years without reports of side effects in infants, according to NHS guidance updated in 2025.