Propolis or bee glue is a resinous mixture that honey bees produce by mixing beeswax with exudate gathered from tree buds, sap flows, or other botanical sources. It is used as a sealant for unwanted open spaces in the hive. 

The National Institutes of Health rates propolis as "possibly effective" for treating cold sores, genital herpes, and post-surgery mouth pain. Propolis is also used to make cough drops for cough and throat irritation.