We studied 104 medical student from the UANL, with symptoms of perenneal allergic rhinitis, including only 30 patients for this study; seven patients with loratadin 10 mg, eight with loratadine 20 mg and 15 with terfenadine 120 mg/day/21 days, 20 mg of loratadine and 120 mg of terfenadine demonstrated significant decrease of the symptoms (P). Two patients had collateral effects with terfenadine, but terfenadine were more effective than the loratadine in the reduction of the skin reactivity.