From Resin to Remedy: How Honey Bees Craft and Use Propolis
Propolis, the remarkable "bee glue," begins its journey as plant resin and transforms into a powerful tool that honey bees use to protect their hives. This sticky substance, with its antimicrobial properties and adaptability, plays a vital role in hive maintenance—sealing cracks, regulating humidity, and creating a protective barrier against pathogens. Beyond the hive, propolis has been valued for centuries for its medicinal properties, used in everything from ancient wound care to modern skincare products. In this blog, we explore how bees collect and process resin, the fascinating chemistry behind propolis, and its extraordinary benefits for both bee and human health.
The Art of Handling Propolis
Propolis changes consistency with the seasons, affecting how beekeepers manage hives. In summer, it’s as stretchy as gum, pulling and elongating as frames are separated. In fall and winter, it hardens, causing a distinct pop or crack sound when the hive is opened. Despite these changes, its purpose remains constant: sealing frames, empty spaces, and boxes to maintain the hive's ideal temperature and humidity while providing honey bees with an “external immune system.”
Working with propolis can make beekeeping challenging. Using a hive tool effectively requires careful technique to avoid disturbing or harming the bees. In summer, when propolis is sticky and pliable, the hive tool must glide frames apart to stretch the propolis until its breaking point. In colder months, when it becomes brittle and cracks, subtle and controlled movements are needed to minimize abrupt sounds that might cause a colony to be more difficult to inspect.
This photo shows the elastic, sticky nature of propolis during the hot summer months.
How do Bees Collect Resin?
Honey bees do not collect propolis in its final form. Instead, they gather plant resins—the raw material needed to produce it. These resins are primarily sourced from conifers but are also collected from various other trees, such as aspen, birch, willow, and poplar, as well as flowering plants like creosote bush, poison ivy, poison oak, sunflower, balsam root, and parsley (all dependent on region).
Only a small number of worker bees are responsible for collecting resin to produce propolis. Because resin hardens after being released by plants, bees must gather it fresh or on warm days when it remains soft and pliable. Upon finding a suitable resin source, a worker bee bites off small chunks, chews them, and mixes in saliva to make the resin more workable. Once softened, she stores the sticky, rounded piece in her pollen baskets (corbicula) for transport back to the hive.
This worker bees has full pollen baskets. Except it’s not pollen, but resin!
Tree resins can vary in color, ranging from white, tan, and brown to red and black, and are typically found on leaf buds, twigs, or bark. These resins serve as a natural defense mechanism for plants, protecting them from insects and pathogens with species-specific chemical compounds. Despite their diversity, all resins share two common properties: they are water-insoluble and harden when exposed to air—though these processes are moderated within the carefully controlled environment of a honey bee hive.
The Transformation of Resin to Propolis
When the resin-collecting bee returns to the hive, she requires help from other workers to unload her sticky cargo. Unlike pollen, which she can easily kick off into a cell, resin must be bitten off by other bees. These chunks are then passed along to additional workers for processing into propolis.
The final product is a blend of resin, beeswax, saliva, and a small amount of pollen. The proportions of beeswax and saliva added depend on the resin's source. On average, propolis consists of about 50% resin, 30% wax, 10% essential oils, and 5% pollen. The remaining 5% includes amino acids, vitamins, and minerals, likely derived from nectar collected by the bees.
Antimicrobial Properties of Propolis
Plant resin doesn’t just supply honey bees with physical advantages, it also brings chemical ones as well. Since the plant is producing the resin as a band-aid to an injured branch, or as a preventative measure to deter any insect mandibles, it clearly has vital chemicals that allow it to be the “immune system” of the plant. Resins are antibacterial, antifungal, antiviral, and anti-inflammatory. Honey bees know this full well and take advantage of these properties—and what better way to do so then smearing this substance in every nook and cranny of a hive. This protective, water-proof envelope within the hive gives the bees an external, second immune system of their own.
In a wild honey bee colony, the workers will form a wide ring of propolis surrounding the base of the comb’s attachment point. It can be inches wide and multiple layers deep to create a layer of insurance that prevents microbes from crossing the barrier. In managed Langstroth hives, such as the ones we have at Buddha Bee, the bees place propolis on almost every wooden surface. They use it like caulk to fill cracks, glue together the moveable frames, strengthen wax combs, sequester unwanted substances, or change their entrance size.
An Aside About Mummified Mice: In late fall, we install entrance reducers on all our hives at Buddha Bee. This practice helps insulate the hive and, more importantly, makes the entrance easier to defend as the colony prepares for winter. During this time, the bees focus more on staying warm than on fending off invaders like mice, voles, or even snakes, which may try to nest in the warm, insulated boxes. While bees can sting a mouse to death, they cannot remove its carcass from the hive. In such cases, they use propolis to encase the body in a thick layer, sealing it off to prevent the spread of germs and disease.
Reduce, Reuse, Recycle
Propolis is made on an as-needed basis and is not stored in the hive for consumption like pollen or nectar. During colder months, when bees rarely leave the hive and fresh resin is scarce, they often reuse existing propolis. Workers remove it from one area and transport it to where it's needed elsewhere in the hive. Collecting resin and transforming it into propolis is an energy-intensive process, so reusing it conserves energy while ensuring the hive remains properly sealed as it prepares for winter.
The video below is from Christopher Wren’s YouTube channel and shows the process a honey bee goes through to collect reused propolis. The process of resin collection at the plant source would likely be somewhat similar! Chris is known for his website blog, TrogTrogBee. To see some super cool photos detailing the propolis recycling process, check out his blog post Recycling Propolis.
The Human Demand for Propolis
Mapping the honey bee genome revealed that honey bees have fewer immune-specific genes than most other insects. Instead of relying on a robust bodily defense system, honey bees use propolis as an extension of their immune system. This evolutionary adaptation allowed the species to focus less on internal immunity by leveraging the protective properties of plant resins.
Humans eventually recognized the connection between propolis and honey bee health. Propolis is now found in man-made products such as toothpaste, skin creams, salves, tinctures, syrups, and elixirs. While not officially classified as a therapeutic agent in conventional medicine, its use in healing dates back thousands of years. The Ancient Egyptians used propolis for medicinal purposes and in mummification. Ancient Greeks applied it to wounds and skin conditions. Roman soldiers carried balls of propolis into battle for its wound-healing and analgesic (numbing) properties. The Incas used it to treat infections. Historical accounts of its use are extensive and there are endless preparations that can be found today.
Propolis is prized for its antimicrobial properties, effective against fungal, viral, gram-positive, and gram-negative bacteria. While gram-positive bacteria have thick cell walls (that make them ironically more pervious), gram-negative bacteria's thinner walls (that make them ironically less pervious) allow more resistance to antibiotics and human antibodies, accelerating antibiotic resistance. Propolis can complement conventional treatments, often working synergistically with antibiotics to enhance effectiveness and slow resistance. Research also highlights propolis' potential in cancer treatment. It may inhibit cancer cell growth through multiple pathways and boost the efficacy of chemotherapy and radiation while reducing drug side effects. Though promising, further studies are needed to confirm its role as a complementary treatment, and not a replacement, for conventional medicine.
Sources:
American Bee Journal, Volume 158 No 10, October 2018, pp. 1155-1158.
https://trogtrogbee.blogspot.com/2018/05/recycling-propolis.html
https://www.beeculture.com/processing-propolis-part-1/
https://pmc.ncbi.nlm.nih.gov/articles/PMC10059947/#:~:text=Propolis%20exerts%20anticancer%20effects%20primarily,invasion%20and%20metastasis%20of%20tumors
https://pmc.ncbi.nlm.nih.gov/articles/PMC3872021/