Bees create propolis by collecting a resinous sap from trees and then mixing it with wax back at the hive. They use this material much the way people use caulk: to seal their homes. Chemically, propolis is exceedingly complex and contains a rich variety of potent terpenes and benzoic, caffeic, cinnamic,and phenolic acids. It's also high in flavonoids, which by themselves may account for many of the benefits attributed to propolis-and some researchers refer to propolis as a type of flavonoid.
Propolis acts against viruses, which antibiotics do not. A number of medical journal reports have discussed the role of propolis in fighting upper respiratory infections, such as those caused by the common cold and influenza viruses (Focht J, Arzneimittel-Forschung, Aug. 1993;43:921-3). Other investigators have reported that the cinnamic acid extracts of propolis prevent viruses from reproducing, but they worked best when used during the entire infection (Serkedjieva J, Journal of Natural Products, March 1992;55:294-302).
Underpinning many of the benefits of propolis is that some of its components,like the flavonoids and ethanols, function as antioxidant free-radical scavengers. A study published in the Journal of Ethnopharmacology (Jan. 1994;21:9-13)noted that some of the antioxidant phenols in propolis functioned similarly to vitamin E. In another article, researchers described that propolis had anti-inflammatory properties and that it could also prevent blood clots(Drugs Under Experimental & Clinical Research, 1993; 19:197-203).