Honeybees gather propolis, a resin, from tree bark and leaves.
They combine this resin with nectar, creating a mix of wax, pollen and bee bread. They then use this substance to seal their hives, protecting it from outside contaminants. They also use propolis at the entrance to the hive to sterilize themselves as they come and go. While propolis is just now enjoying a rediscovery, its usefulness can be traced back to the time of Hippocrates, who used it to heal sores and ulcers, internally and externally. Through the ages historical documents record its use.