The bees gather viscid resinous substances from leaf buds of poplar, birch, aspen and other trees. Having brought it in the beehive, they mix it with wax and internal glands secretions. In such way the propolis is created. It is just the reason of practical absence of the different microorganisms inside the beehives. This quality was noticed as far as long ago - Ancient Egyptians used the propolis for preparation of medicines.
Propolis is known to be rather strong anaesthetic. Thereof effect is 5 times more than novocaine. It contains up to 30 % phenolic compounds preventing the process of aging and cancer.