Propolis or bee glue is a resinous mixture that honey bees produce, mixing saliva and beeswax with exudate gathered from tree buds, sap flows or other botanical sources. It is used as a sealant in open spaces of the hive and covers every surface. Propolis is antiviral, antibacterial and antifungal.
Its color varies, depending on its botanical source, the most common being dark brown. Propolis is sticky at and above room temperature; at lower temperatures, it becomes hard and very brittle. Beekeepers assumed that bees sealed the beehive with propolis to protect the colony from the elements, such as rain and cold winter drafts; however, 20th-century research has revealed that bees not only survive, but thrive with increased ventilation during the winter months, throughout most temperate regions of the world. It is now believed that propolis reinforces the structural stability of the hive, reduces vibration, makes the hive more defensible by sealing alternative entrances, prevents diseases and parasites from entering the hive, inhibits fungal and bacterial growth and prevents putrefaction within the hive.
Bees usually carry waste out of and away from the hive; however if a small lizard or mouse, for example, finds its way into the hive and dies there, bees may be unable to carry it out through the hive entrance. In that case, they would attempt instead to seal the carcass with propolis, essentially mummifying it and making it odorless and harmless.
*If you are allergic to bee venom, you may have a reaction to propolis products.