In order to elucidate the mast cell changes challenged by various antihistaminic preparations and its role to the mast cells challenged by inflammation, male albino rats weighing 120-130gm were used for this investigations. Benadryl hydrochloride, Phenergan hydrochloride and Chlor-Trimeton maleate were choosed for antihistaminic challengers and ultraviolet ray was irradiated for an inflammatory challenger. 1. When rats were challenged by various antihistaminics the numbers of mast cell reached to the least after 2 days and later followed by an increasing mast cell numbers. 2. The mast cell changes were severer in order of Phenergan hydrochloride, Benadryl hydrochloride and Chlor-Trimeton maleate. 3. Degranulated mast cell was proportionally increased as the numbers of mast cell decrease after being challnged by antihistaminics and also it was decreasing when the numbers of mast cell were re-increasing