Purpose: The present paper reports the antianaphylactic, antihistaminic and mast cell stabilization activity of Ocimum sanctum leaf extract on various experimental models. Methods: After optimizing the dose the extract was tested for its therapeutic activity using Wistar rats and Duncan Hartley guinea pigs. The antianaphylactic activity was investigated in rats using the active anaphylaxis model. The effect on mast cell stabilization was performed by ex vivo challenge of antigen in sensitized rat intestinal mesenteries. Antihistaminic activity was studied in guinea pigs using histamine-induced bronchospasm where preconvulsive dyspnea was used as an end point following exposure to histamine aerosol. Results: The findings from various studies reveal that the antihistaminic and antianaphylactic activity of extract which is mainly due to its mast cell stabilizing potential, suppression of IgE, and inhibition of release of inflammatory mediators Conclusion: Thus use of Ocimum sanctum leaves proved the strong rationale behind the mentioned therapeutic activities.