Histamine

Histamine is a biogenic amine and primary mediator of mast cell and basophil degranulation in allergic, inflammatory, and immune activation responses, acting through H1-H4 receptors to amplify vascular permeability, smooth muscle contraction, and immune cell recruitment. In saliva, histamine reflects local oral mucosal mast cell activity and systemic histamine release associated with inflammation, food intolerance, exercise-induced urticaria, and overtraining-related immune dysregulation. Maintz and Novak (2007) characterised histamine's broad role in immune activation relevant to sport and health monitoring.