in order to show the antiallergic properties conferred to ocimum tenuiflorum l., its possible influence on the anaphylactic mediators and on bronchial spasm induced by histamine, as well as its possible effect as bronchodilator, were studied. wistar male rats were used in the passive cutaneous anaphylaxis test. they were administered the extract at doses of 250, 500 and 1000 mg/kg by oral route for 10 days, using ketotiphen 3 mg/kg as a positive control. the anaphylaxis intensity was determined by quantifying the amount of extravasated evans blue. the bronchodilator and protective effect of bronchial spasm was determined in hartley male guinea pigs by inducing bronchoconstriction through the intravenous administration of histamine and determining the bronchial pressure. as a result, it was found that the frozen dried aqueous extract of ocimum tenuiflorum l. inhibited the passive cutaneous anaphylaxis and that it did not present a protective effect of the bronchial spasm induced by histamine. no bronchodilator properties were observed in the pharmacological model used.