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(also bee glue), a sticky resinous substance produced by honeybees.
The bees apply propolis to the walls of the hive and seal cracks with it. Propolis has a bitter taste and a syrupy consistency, and it is yellow or brown in color. When stored, it thickens and hardens into a brittle (rosinous) dark-brown mass. Propolis melts at 80°–104°C and crumbles at 15°C. It dissolves in hot methyl alcohol, petroleum ether, liquid ammonia, acetic acid, and a 70-percent solution of ethyl alcohol. Its chemical composition is 50–55 percent plant resins, 8–10 percent essential oils, and about 30 percent wax. About 100–150 g of propolis is collected from each hive in a season. It is stored in the form of balls of 150–200 g in parchment paper. Propolis has an antimicrobial effect and is used in medicine and veterinary practice. Ointments are made from it to treat wounds, eczema and certain other conditions. Propolis is an ingredient in corn plasters.