Histamine release refers to the process by which mast cells and basophils release histamine, a biogenic amine that plays a key role in immune responses, particularly during allergic reactions. This release can lead to various physiological effects such as vasodilation, increased vascular permeability, and stimulation of gastric acid secretion, connecting directly to the effects of antihistamines and decongestants, which are often used to counteract these actions.