Propolis is made by honey bees using plant resins collected, here in Britain, from conifers, poplars, horse chestnut buds, and so on. Honey bees carry propolis back to their nest on their pollen baskets and, once there it’s taken by the house bees (young workers) who mix it with a little wax and some pollen and spread it around the whole of the inside of their nest. Every surface is covered with a thin layer of propolis.
Honey bees also use propolis as a sealant, and any gap smaller than 4 to 6mm will be plugged closed. In the winter they’ll sometimes reduce the size of their entrance with a propolis seal which, once cool and set quite hard, is very difficult to break.
Some colonies use more propolis than others and will coat everything inside their nest with a very thick sticky layer, which is a good reason for beekeepers to wear washable gloves – propolis almost always stains yellow or orange. It can, on a sunny day, have a wonderful smell and can taste like a whole garden full of flowers – this from the different pollens collected by the bees.
Propolis has antibacterial and antifungal properties so, when the bees line their nests, they’re making sure it’s clean and that it stays clean. They cover stray large insects and small mammals with it too, if they can’t haul them out through the entrance. Many a beekeeper finds a bald, mummified, bumble bee queen in one of their hives in Spring and some may even find a mouse or shrew skeleton that’s been similarly treated.
Humans have used propolis since at least Egyptian times, when it was used in mummification. Stradivarius used propolis as an ingredient for his varnish, as do some modern instrument makers. It used to be added to treatments for mouth ulcers and wound care and can still be found in some toothpastes and mouthwashes from herbalists.