Cetirizine is classed as a non-drowsy (non-sedating) antihistamine, but it does make some people drowsy. In clinical trials, this side effect appeared to be related to the dose of cetirizine, with higher dosages increasing the risk of feeling drowsy. 1.9% of children aged 6 to 11 years experienced drowsiness with 5mg of cetirizine and 4.2% of children experienced drowsiness with 10mg of cetirizine. Up to 14.3% of adults may be affected by drowsiness with cetirizine.