Cetirizine typically starts to work within 20 to 60 minutes after taking it and provides allergy relief for about 24 hours. You should start to notice relief from symptoms such as sneezing, runny nose, itchy and watery eyes, and itchy nose or throat within an hour. Taking it on an empty stomach may lead to faster onset, while food may slightly delay its effect. Most sources agree cetirizine reaches its maximum effect around 1 to 2 hours after ingestion. It is considered a non-drowsy antihistamine, although it may cause drowsiness in some individuals. In summary:
- Starts working: within 20 to 60 minutes
- Maximum effect: around 1 to 2 hours
- Duration: about 24 hours
This makes cetirizine a convenient option for once-daily allergy symptom relief.
