Food Supplements - Bee Propolis - Source

Bee propolis is very difficult to harvest and thus commands a high price.

Beekeepers slide small inserts into the hive, which look like cracks to bees. The bees respond by "fixing" the "crack" and fill the inserts with propolis.

Propolis may also be scraped out of the hive. However, this results in an inferior, contaminated product containing unwanted bee by-products.