Propolis

Propolis, also called bee glue, is a resinous mixture that honey bees make by combining saliva and beeswax with exudate gathered from tree buds, sap flows and other plant sources. Bees use it to seal small gaps in the hive, generally those under about six millimetres, to reinforce the structure, to insulate it and to narrow the entrance. They may even entomb an intruder they cannot carry out, such as a dead mouse, in propolis to stop it rotting. Its colour is usually dark brown but ranges across green, red, black and white depending on the resin source, and it is sticky above about 19 degrees Celsius and hard and brittle when cold. Composition varies with region and season; temperate propolis is roughly half resins and balsams, a third wax, a tenth essential oils and a little pollen. It has traditional medicinal use without clinical evidence, and some string instrument makers use it in varnish.