1. Something that causes a contraction of tissues, arrest of secretion, or control of bleeding.
2. A substance or preparation; such as, alum, that draws together or constricts body tissues and is effective in stopping the flow of blood or other secretions.

Astringents act as protein precipitants; they arrest discharge by causing shrinkage of tissue.

Some astringents; such as, tannic acid, have been used in treating diarrhea; others; such as, boric acid and sodium borate, help relieve the symptoms of inflammation of the mucous membranes of the throat or conjunctiva of the eye.

Skin lotions often contain astringents; such as, aluminum acetate that help to reduce oiliness and excessive perspiration. Witch hazel is a common household astringent used to reduce swelling.

Styptic pencils, used to stop bleeding from small cuts, contain astringents. Zinc oxide and calamine are astringents used in lotions, powders and ointments to relieve itching and chafing in various forms of dermatitis.