Astringents

substances which, acting on the mucous membranes or damaged skin, cause partial coagulation of the proteins of the superficial layers of tissue with the formation of proteinaceous films that protect lower-lying tissues from the influence of irritating agents. Blood vessels constrict, and their walls harden during this process; as a result, the exudation of fluid and edema are reduced.

Organic astringents include tannin, obtained from gallnuts, and other substances contained in plants (the bark of the oak, the fruit of the whortleberry, the leaves of sage, the flowers of the chamomile, and so on), as well as weak solutions of alcohol and Formalin. Among the nonorganic types are certain silver preparations, such as diluted solutions of silver nitrate (lapis), and preparations of zinc and lead (lead water), of bismuth (basic bismuth nitrate, xeroform, and others), and of aluminum (Burow’s solution). Astringents are applied externally for inflammatory illnesses of the skin and mucous membranes and are given internally for certain illnesses of the gastrointestinal tract (gastritis, colitis, and stomach ulcer). Astringents are also used as an antidote for certain types of poisoning, especially by alkaloids (atropine, scopolamine, and others).