It is my understanding that propolis is found in trees within the poplar family: poplar, aspen, and conifers (pine trees). Only bees in areas with those types of trees will produce beeswax that contains propolis.
Unfortunately, some people turn out to be allergic to beeswax— in fact, they are reacting to the propolis in the beeswax. The most common reaction is a rash and swelling around the mouth and lips of a person who is using lip balm made with beeswax.
Fortunately, there are alternative (plant) waxes, such as candelilla wax that are safe for those who can’t use beeswax, and for vegans.