ASTRINGENT

any of a group of substances that tend to shrink mucous membranes and raw surfaces and to dry up secretions. Astringents are usually classed according to their mode of action into: (1) those that decrease the blood supply by narrowing the small blood vessels (e.g., adrenaline and cocaine); (2) those that abstract water from the part (e.g., glycerol and alcohol); and (3) those that coagulate the superficial layers into a crust (e.g., metallic astringents, such as calamine or alum). Used in medicine to reduce swollen mucous membranes that result from inflammations of the nasal, alimentary, and urinary passages, astringents are also frequently employed to dry up excessive secretions and (in this connection often known as styptics) to stop the oozing of blood.