About Fexofenadine Second Generation H1 Antagonist, Antihistamine. Mechanism of Action of Fexofenadine Fexofenadine blocks one type of peripheral receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine (Histamine is released from histamine-storing cells (mast cells) and then attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cell to be "activated," releasing other chemicals that produce the effects that we associate with allergy, e.g., sneezing.) and the allergic symptoms produced by it.