The aim of this double-blind study was to evaluate the effectiveness of cetirizine and loratadine versus placebo in patients with allergic rhinitis. The study included a total of 90 patients suffering from moderate to severe allergic rhinitis as determined by a symptom score, with hypersensitivity to house mites and with high IgE. The study lasted 7 weeks, including 1 for pretreatment, 4 for treatment and 2 posttreatment (washout). During the study, each patient received either one tablet of placebo, 10 mg of cetirizine or 10 mg of loratadine daily. The evaluation was carried out by rhinomanometry to analyze the symptoms on days 1, 15, 29 and 43. The nasal cytology was analyzed on days 1 and 29. For statistical analysis we used the Mantel-Haenszel method and chi-square test. We found that antihistamines showed good effectiveness in improving the symptomatology in patients with allergic rhinitis. The improvement by rhinomanometry and by symptom score versus placebo was good. It was concluded that both antihistamines were significantly superior to placebo and that cetirizine performed better in comparison to loratadine versus placebo, although not as statistically significant.