Bee propolis: what it is, what the science shows, allergy risks and FDA rules

Bee propolis is a sticky resin that honey bees gather from tree buds, mostly poplars and cottonwoods across much of the United States, and blend with wax to seal and line the inside of the hive. In the lab its extracts kill or slow many bacteria and fungi, but good clinical evidence in people is limited: the FDA has not approved propolis for any medical use or authorized any health claim for it, and it is a well documented cause of skin allergy. This guide covers what propolis is, what it does for the colony, what the research actually supports, how federal supplement rules apply, the allergy risks and how beekeepers harvest it cleanly.

What is propolis and why do bees make it?

The word comes from Greek pro, in front of, and polis, the city. Beekeepers call it bee glue, because it cements frames, inner covers and supers together and makes a hive tool the first thing you reach for.

A material that changes with temperature

Propolis is hard and brittle when cold and soft and gummy when warm. Its color runs from yellow-green to dark brown depending on the trees the bees worked, and it smells strongly of resin. In alcohol it separates into an insoluble waxy part and a dissolved fraction, the “balsam,” which holds most of the compounds researchers study and forms the base of commercial tinctures.

How the colony uses it

The reference review on the subject, by Michael Simone-Finstrom and Marla Spivak of the University of Minnesota, published in Apidologie in 2010, lists several jobs propolis does in the nest:

• Sealing cracks and narrowing entrances. Bees fill gaps, shrink the entrance and smooth the surfaces where comb is attached. In a Langstroth hive, any gap narrower than bee space ends up glued shut.
• Building a propolis envelope. A wild colony studied in a hollow tree had lined its cavity walls with a thin layer about 0.01 to 0.02 inch (0.3 to 0.5 mm) thick.
• Embalming intruders. A dead mouse or large insect too heavy to haul out gets covered in propolis, which limits decay inside the hive.
• Imprisoning pests. Cape honey bees in South Africa confine the small hive beetle, Aethina tumida, in “propolis prisons” that keep it from breeding. That beetle has been established in the United States since the late 1990s and is a familiar pest in Southern apiaries, but American colonies do not control it this way, so beetle traps and strong colonies remain the beekeeper’s job.

Not every honey bee species does this. The same review notes that the Asian honey bee, Apis cerana, is not thought to use resin at all, while the western honey bee, Apis mellifera, uses it heavily. To see where resin collecting fits among the other tasks in the hive, read our guide to the honey bee colony.

Part of the colony’s social immunity

Propolis is more than caulk. Researchers describe it as part of social immunity, the colony’s collective defense against disease. Simone-Finstrom and Spivak report that after seven days, young bees in colonies whose walls were coated with propolis expressed two immune-related genes at lower levels, a likely sign of fewer microbes in the nest.

A University of Minnesota field study led by Renata Borba, published in the Journal of Experimental Biology in 2015, followed full-size colonies with and without a natural propolis envelope. Bees living with the envelope had lower and steadier baseline immune gene activity in summer and fall, with no difference in measured pathogen or parasite levels. After one of the two winters, colonies with an envelope were stronger and had higher vitellogenin levels.

Spivak’s group then asked whether beekeepers could bring the envelope back. In a 2024 study in PLOS ONE led by Maggie Shanahan, Langstroth boxes with roughened, grooved inner walls stored the most propolis, boxes fitted with propolis traps stored less, and standard smooth boxes stored the least. The European foulbrood bacterium was detected significantly less in rough-box colonies on migratory operations, while varroa showed only a non-significant downward trend. One cost appeared: in the first migratory year, small colonies in rough-walled boxes made about 20 kg (44 lb) less honey than controls; the gap disappeared the next year, in boxes already lined with propolis. Survival did not differ. Speaking at NC State University in 2024, Spivak reported that colonies with a propolis envelope painted on interior walls had significantly less chalkbrood and American foulbrood, and that grooved Langstroth boxes have been shown to increase colony size in commercial almond pollination.

In lab tests, propolis extracts inhibit Paenibacillus larvae, the bacterium behind American foulbrood, and in a Petri dish a 10% ethanol extract killed every varroa mite tested. The 2010 review stresses that feeding propolis extract to colonies reduced the number of diseased larvae without curing American foulbrood, and that the varroa result has stayed in the lab. Propolis is not a treatment for varroa mites or foulbrood. Use EPA-registered varroa products according to their label, and contact your state apiarist if you suspect American foulbrood, which many states regulate.

How do honey bees collect resin?

The trees American bees visit

In temperate climates, poplars (Populus) are the main resin source, and in North America that group includes cottonwoods and aspens. Where they are scarce, bees turn to pines, birches, elms, alders, beeches and horse chestnuts. They favor buds and young leaves, which carry sticky resins that protect growing tissue. In the tropics, bees use different plants, such as Clusia flowers or the Brazilian shrub Baccharis dracunculifolia.

The work of resin foragers

Only a small fraction of foragers collect resin, and they appear to specialize, possibly with a genetic component. Observations compiled in the 2010 review describe slow, fiddly work:

1. The forager bites off a piece of resin with her mandibles.
2. She works it and passes it from leg to leg into the pollen baskets on her hind legs.
3. She repeats this until she has a full load, which usually takes about seven minutes but can take fifteen minutes to an hour depending on the weather.
4. Back at the hive she cannot unload herself. Other workers pull the resin from her baskets, usually in about fifteen minutes, but it can take one to seven hours or even overnight.
5. Those workers blend the resin with wax and apply it where the colony needs it.

A bee never carries resin and pollen on the same trip. Collection happens mostly on sunny days between about 10 a.m. and 3:30 p.m., when warmth makes resin workable, and it is reported to peak from late summer into fall as nectar flows taper off. In the Northeast and Upper Midwest that usually means August and September; in the South and California, with longer seasons, resin collection can stretch further into the fall.

The chemistry comes from the tree

Propolis chemistry largely mirrors the resin it came from, although some volatile compounds evaporate on the way home. That is the key to everything else: cottonwood propolis from a Minnesota apiary and green propolis from Brazil have very little in common chemically.

What is propolis made of?

The “50-30-10-5-5” formula, and why to doubt it

Most websites repeat the same breakdown: about 50% plant resins and balsams, 30% wax, 10% essential and aromatic oils, 5% pollen and 5% other matter. It even shows up in scientific reviews, such as Simona Martinotti and Elia Ranzato’s 2015 paper in Burns & Trauma.

A 2021 scientific note in Apidologie by Antonio and Maria Luiza Salatino traced those numbers through decades of copying back to a source published before 1934, probably about European propolis, whose data have never been verified. Real measurements vary enormously:

Component	Often quoted	Actually measured (Salatino, 2021)
Wax	30%	from under 10% (notably Brazilian green propolis) to 87% (a Moroccan sample)
Volatile oils	10%	rarely above 1%, with exceptions of 3.5% (India) and 8.5% (southern Brazil)
Resins and balsams	50%	above 70% in most of 20 Italian samples

The authors cite Brazil’s quality standards as an example of real benchmarks: no more than 25% wax, 5% ash and 8% moisture, and at least 5% phenolic compounds and 0.5% flavonoids. The United States has no federal standard of identity for propolis, so there is no equivalent benchmark on American labels. There is no single “propolis,” only many propolises.

Up to 300 compounds in one sample

According to Simone-Finstrom and Spivak, a single sample can contain up to 300 chemical compounds. The main families are:

• Flavonoids, the most studied. In poplar propolis, pinocembrin, galangin and pinobanksin are associated with antimicrobial activity.
• Phenolic acids and their esters, including caffeic acid phenethyl ester (CAPE), a lab favorite.
• Terpenes, dominant in some Mediterranean propolis.
• Origin-specific compounds, such as artepillin C in Brazilian green propolis or prenylated benzophenones in red propolis.

The practical upshot: a study on one propolis tells you little about the next unless its chemistry was analyzed.

Green, brown or red propolis: what is the difference?

Martinotti and Ranzato group propolis by origin:

Type	Where	Main plant source	Marker compounds
Poplar (brown) propolis	North America, Europe	poplar and cottonwood buds, sometimes conifers	flavonoids and other polyphenols
Green propolis	southeastern Brazil	Baccharis dracunculifolia	artepillin C
Red propolis	Cuba, Venezuela, Brazil	Clusia flowers (Cuba, Venezuela); other plants in Brazil	prenylated benzophenones; isoflavonoids in Brazilian red
Mediterranean propolis	Greece, Malta, Crete, southern Italy	probably conifers (cypress, pine)	diterpenes
Pacific propolis	Taiwan, Japan	Macaranga	prenylated flavanones

Is Brazilian green propolis better?

Green propolis often sells at a premium and is marketed as superior. No evidence shows it is better for human health; it is different. It is low in wax, which makes it easier to extract, and it is heavily studied for artepillin C. Simone-Finstrom and Spivak report that it inhibited the American foulbrood bacterium more strongly in the lab than poplar propolis from Minnesota, although both were active, which mainly shows how much origin matters.

If you want a domestic product, look for the country, and ideally the state, of collection on the label.

What are the benefits of propolis according to research?

Separate three levels of evidence: test tubes, animals and controlled trials in people. For propolis, the first two are plentiful and the third is thin.

Well established in the lab

Propolis extracts show measurable antibacterial, antifungal, antioxidant and anti-inflammatory activity in vitro. That activity varies by geography, as Simone-Finstrom and Spivak point out, because it depends on the plants the bees visited. An effect in a dish says nothing about the dose a person would need or what happens to those compounds after you swallow them.

Wounds and skin: mostly animal data

Propolis shows up in ointments, creams, lip balms and dressings. Martinotti and Ranzato’s 2015 review on wound healing presents it as a promising lead for wounds and burns, but the evidence comes mainly from lab and rodent studies. The authors list the gaps themselves: many studies never characterize the propolis tested, and bioavailability, product stability and safe, effective doses have not been established. They mention a 2013 estimate of a safe oral intake of about 1.4 mg per kg of body weight, roughly 70 mg a day; no health agency has adopted it as a reference dose.

Mouth sores from cancer treatment: promising, not settled

The best documented human use is oral mucositis, the painful mouth inflammation caused by chemotherapy and radiation. A 2022 systematic review from Universitas Padjadjaran in Indonesia, in the International Journal of Applied Pharmaceutics, concluded that propolis reduced mucositis severity in the studies it included, almost all without reported side effects. It covered only English-language papers from 2016 to 2021 and mixed animal studies with small trials. A 2021 practice guideline from German-speaking cancer centers, in Integrative Cancer Therapies, calls propolis promising for grade 2 and 3 mucositis, citing one meta-analysis of five small trials and one further trial. The evidence is moderate at best, and this is a decision for your oncology team, never self-treatment.

What has not been shown

Boosting immunity, preventing colds and flu, protecting the liver, heart or gut, acting as a “natural antibiotic”: none of these has been backed by trials strong enough to support an approved drug use or an authorized health claim. When a propolis supplement says it “supports immune health,” remember that this kind of structure/function statement is written by the manufacturer and is not reviewed or approved by the FDA, and that a blend may owe any such claim to added vitamin C or zinc rather than to propolis.

Does propolis help a sore throat?

Throat sprays, lozenges and syrups are the propolis products most Americans see in drugstores and natural food stores. An honest summary:

• There is no FDA-approved use or authorized health claim for propolis and the throat.
• Most sore throats are viral and improve on their own within about a week. Whatever you take in that window tends to look as if it worked.
• Products usually combine several ingredients, such as honey, elderberry, zinc, essential oils or vitamin C, so any effect cannot be credited to propolis.
• Honey soothes a throat too. For what honey can and cannot do, see the health benefits of honey.

If you are not allergic, using a spray for a few days is unlikely to cause harm. See a doctor or urgent care clinic if you have a high fever, trouble swallowing or breathing, swollen tender glands, or symptoms that are getting worse. Strep throat needs a test and a prescription antibiotic, and no propolis product replaces that.

How does the FDA regulate propolis supplements?

A dietary supplement under DSHEA

Propolis capsules, tablets, tinctures and sprays sold to be swallowed are generally marketed as dietary supplements. Federal law, as amended by the Dietary Supplement Health and Education Act of 1994 (DSHEA), defines a dietary supplement as a product intended to supplement the diet that contains one or more dietary ingredients, a list that includes herbs and other botanicals, “a dietary substance for use by man to supplement the diet,” and concentrates or extracts of these. It must be labeled as a dietary supplement and not presented as a conventional food.

The key point for consumers: the FDA “is not authorized to approve dietary supplements for safety and effectiveness before they are marketed.” Many products reach shelves without the FDA ever being notified. The agency acts after the fact, through warning letters, recalls and safety alerts, and it advises consumers to talk to a doctor, pharmacist or other health professional before using a supplement.

Structure/function claims and the disclaimer

The FDA recognizes several kinds of label claims: health claims, which require FDA authorization or a qualified health claim review; nutrient content claims; and structure/function claims. No authorized or qualified health claim exists for propolis.

What you will see instead are structure/function statements, such as “supports immune function.” Under 21 CFR 101.93, a company using one must notify the FDA no later than 30 days after it first markets the product, and the label must carry this disclaimer:

This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

In a December 2025 letter to industry, the FDA said it would use enforcement discretion on the old requirement that the disclaimer appear on every panel where a claim appears, while it considers changing the rule. The disclaimer itself, linked to each claim, is still required.

When a claim crosses the line

The same regulation defines a disease claim as one that says, explicitly or implicitly, that a product diagnoses, mitigates, treats, cures or prevents a disease. A supplement making that kind of claim is treated as an unapproved new drug.

That is not theoretical for bee products. On October 23, 2020, the FDA and the Federal Trade Commission jointly sent a warning letter to Beepothecary LLC, an Ohio company selling an “Elderberry, Honey & Propolis Syrup” and other hive products. Social media posts had called propolis “ANTIVIRAL” and promoted it against COVID-19. The FDA cited the products as unapproved new drugs and misbranded under the Federal Food, Drug, and Cosmetic Act. The FTC added that any claim a product prevents, treats or cures disease must be backed by “competent and reliable scientific evidence,” which did not exist.

Allergen labeling

Propolis is not one of the nine major food allergens that must be declared under federal allergen labeling law, so a product does not have to carry a bee product allergy warning by law. Read the full ingredient list rather than relying on a warning box.

Reporting a problem

If you have a reaction to a propolis supplement, tell your doctor and report it to the FDA through the Safety Reporting Portal (safetyreporting.hhs.gov), which takes reports on the quality or safety of dietary supplements from consumers and health professionals.

Propolis side effects, allergy and who should avoid it

Skin allergy is the main risk

Propolis is one of the best documented natural contact allergens. The North American Contact Dermatitis Group, which pools patch test results from specialty clinics in the United States and Canada, compared propolis test materials from 2019 to 2022 in a study published in Dermatitis in 2026. With a Chinese propolis, 3.7% of tested patients reacted in 2019 (84 of 2,260). When a Brazilian propolis was substituted in 2020, the positive rate jumped to 14.7% (271 of 1,838). After a switch back to another Chinese propolis, it fell to 2.2% in 2021 and 2022 (66 of 3,052). These are patients already referred for suspected skin allergy, not the general public, but the swing shows how strongly the origin of propolis affects reactions.

A European study of 1,470 dermatitis patients in Denmark, Lithuania and Spain, published in Acta Dermato-Venereologica in 2021, found reaction rates to propolis of 1.3% to 5.8%, and that a single propolis test picked up only about half of the allergic patients. A negative test with one sample does not fully rule out allergy.

Propolis rashes can be severe, with blistering where the product was applied. Those most exposed are beekeepers, people who handle beeswax, and violin makers and string players, since propolis is used in some instrument varnishes. For consumers, the risk comes from ointments, lip balms, toothpastes, shampoos, cosmetics and sprays.

Cross-reactions with balsam of Peru, rosin and fragrance

Propolis shares several allergens with balsam of Peru (Myroxylon pereirae), a resin used in fragrances and flavorings. The 2021 European study found co-reactions to balsam of Peru, colophony (rosin, found in adhesive bandages, tapes and some varnishes) or fragrance mixes in 12.5% to 50% of propolis-allergic patients. If you know you react to any of these, avoid propolis.

Swallowed propolis: lips, mouth and, rarely, anaphylaxis

Taken by mouth, propolis can inflame the lips and the lining of the mouth and occasionally cause throat swelling or a widespread rash in someone already sensitized. Severe immediate allergic reactions are rare, but they have been reported. Call 911 if your lips, tongue or throat swell or if you have trouble breathing.

Who should avoid propolis?

Situation	Advice
Known allergy to bee products, including beeswax or royal jelly	do not use
Allergy to balsam of Peru, rosin (colophony) or fragrance	do not use, cross-reaction likely
Pollen allergy, asthma or other allergic conditions	be cautious; ask a pharmacist first
Allergy to bee, wasp or yellowjacket stings	ask your allergist first
Pregnancy and breastfeeding	avoid, since safety data are lacking
Blood thinners or other long-term medications	ask a pharmacist before use
Children	ask a pediatrician; avoid alcohol-based tinctures
Eczema or broken skin over a large area	avoid wide application; patch test first

Testing at home and at the clinic

Before using a propolis cream or balm, dab a small amount on the inside of your elbow and wait 48 hours. Redness, itching or small blisters suggest an allergy: stop, because contact allergy usually lasts for life and later reactions can be stronger. A home test is no substitute for patch testing by a dermatologist or allergist, and if you have used bee products, ask for propolis to be included, ideally with more than one type.

Tincture, spray or capsules: how to choose a propolis product

The main forms

Form	Typical use	Watch out for
Alcohol-based tincture or extract	drops in water or on honey	high alcohol content; stains teeth and fabric
Alcohol-free extract (glycerin or water)	adults avoiding alcohol	strength often lower and rarely stated
Throat spray	mouth and throat	usually combined with other ingredients
Lozenges and syrups	throat	sugar or sweeteners
Capsules and tablets	dietary supplement	check whether the stated milligrams are extract or raw propolis
Raw propolis	chewing, or making a tincture	dose impossible to know; possible debris
Creams, balms, cosmetics	skin and lips	contact allergy risk

Reading the label

A well labeled product should tell you:

1. Where the propolis came from, at least the country, since origin determines chemistry.
2. How much propolis or extract is in each serving, and ideally its phenolic or flavonoid content. A headline figure that does not say whether it means extract or raw propolis is hard to compare.
3. The full ingredient list, so you can spot alcohol, sugars, essential oils and added vitamins.
4. A Supplement Facts panel and serving size, plus the FDA disclaimer next to any structure/function claim.
5. An allergy statement for people sensitive to bee products, even though it is voluntary.
6. A lot number and expiration or best-by date, plus the name and address of the manufacturer or distributor.

Be skeptical of cure claims, COVID or flu prevention claims and products sold only online with no identifiable U.S. company behind them. Those are exactly the claims the FDA and FTC have targeted. The same habits help with honey, as our guide on how to choose honey explains.

How long to take it

No health agency has set a reference dose for propolis. Follow the label, do not exceed it, and avoid taking propolis products continuously or repeatedly all year without checking with a pharmacist or doctor. Propolis sits on the same shelf as other hive products with a similar status, such as royal jelly.

How do beekeepers harvest propolis?

Scraping or a propolis trap

Scraping means collecting propolis from top bars, frame rests and the upper walls of the brood box with your hive tool during inspections. It is usually mixed with wax, wood, bee parts and, on painted equipment, paint. Keep scrapings for your own use or for melting down.

A propolis trap takes advantage of the colony’s urge to seal any gap too narrow to walk through. A flexible, food-grade plastic sheet with narrow slots goes in place of the inner cover or just beneath it. The bees fill the slots to block light and drafts, and the result is much cleaner propolis that pops out easily once frozen.

Harvesting with a trap, step by step

1. Install the trap on strong, healthy colonies after the main honey flow. In the Northeast and Midwest that usually means late July to September; in the Southeast or California, adjust to your local flows. Colonies propolize most as fall approaches.
2. Let in a little light or air above the trap, for example by propping the outer cover slightly or removing insulation, to encourage sealing.
3. Remove the trap once the slots are well filled, usually after several weeks, and before you winterize so the colony is not left under a drafty ceiling.
4. Freeze the trap for a few hours in a clean bag until the propolis is hard and brittle.
5. Flex and tap the trap while still cold over a clean tray; the propolis breaks off in flakes.
6. Pick out debris and store the flakes in a closed glass jar or food-grade bag, away from light, heat and moisture.

Yields depend on the bees, the trees nearby and how many traps you use, but expect a few ounces, roughly tens to a few hundred grams, per hive per year. Simone-Finstrom and Spivak note that selective breeding has reduced the propolizing tendency of managed bees, since beekeepers long preferred colonies that are easy to open. Caucasian bees have a long-standing reputation as heavy propolizers, and colonies of any stock differ widely.

Quality and safety points

• Do not collect during varroa treatment. Some miticides, especially fat-soluble ones, build up in wax and can migrate into propolis. Remove traps before any treatment and put them back only after the treatment is finished and any strips are out, following the EPA-registered product label, which is legally binding.
• Never scrape painted or treated woodwork, and keep propolis from secondhand equipment of unknown history out of anything you sell.
• Clean and store traps after use where wax moths cannot reach them.
• Protect your hands. Many beekeepers become sensitized to propolis over the years. Nitrile gloves cut exposure when scraping or cracking traps.

Selling propolis: what to check first

Rules for selling propolis depend on your state and on how you present the product. State cottage food laws were mostly written for low-risk foods such as honey, jams and baked goods, and many do not extend to tinctures, capsules or other products sold as dietary supplements, which are also subject to federal supplement rules, including current good manufacturing practices. Before you sell, ask your state department of agriculture or health how they classify raw propolis and propolis extracts. Wherever you sell, you can describe where and how it was collected, the trees nearby, its color and aroma. You cannot say it treats, cures or prevents any illness: that would make it an unapproved drug in the FDA’s eyes, as the 2020 warning letter shows. For setting up your extraction space and lot records, see our guide to harvesting honey.

Frequently asked questions

Is propolis FDA approved?

No. Propolis supplements are sold under the Dietary Supplement Health and Education Act of 1994, which does not allow the FDA to approve supplements for safety or effectiveness before they reach shelves. The FDA has authorized no health claim for propolis. A label may carry a structure/function statement with the standard FDA disclaimer, but it may not say propolis treats, cures or prevents any disease.

Does propolis work for a sore throat?

There is no solid clinical evidence that it does. Propolis kills or slows some microbes in lab dishes, but that has not translated into convincing trials in people, and most sore throats are viral and clear up on their own within about a week. See a doctor for a high fever, trouble swallowing or breathing, or a sore throat that keeps getting worse, since strep throat needs a prescription antibiotic.

Who should not take propolis?

Skip it if you react to bee products, balsam of Peru, rosin (colophony) or fragrance, because cross-reactions are common. People with pollen allergy or asthma should be careful, and there are not enough safety data for pregnancy or breastfeeding. Check with a pharmacist first if you take a blood thinner or any long-term medication, and do not give alcohol-based tinctures to children.

How common is propolis allergy in the US?

It is one of the better known contact allergens. In North American Contact Dermatitis Group testing of patients referred for suspected skin allergy, 3.7% reacted to a Chinese propolis test material in 2019 and 2.2% to another Chinese propolis in 2021 to 2022. When a Brazilian propolis was used in 2020, positive results jumped to 14.7%, showing how much the source matters.

What is Brazilian green propolis?

Green propolis comes from southeastern Brazil, where bees collect resin from a shrub called Baccharis dracunculifolia. It is low in wax and rich in artepillin C, a compound missing from the poplar propolis made by most North American colonies. Nothing shows it is better for your health. It is simply different, so studies on green propolis cannot be applied to other types.

Is propolis a natural antibiotic?

Not in the medical sense. Propolis extracts inhibit some bacteria and fungi in the lab, but potency varies with where the propolis came from, and no strong clinical trial shows it treats infections. It never replaces an antibiotic your doctor prescribes. Marketing it as an antibiotic or as a treatment for an illness would make it an unapproved drug under federal law.

How much propolis does a hive produce?

Typically a few ounces a year, roughly tens to a few hundred grams, depending on the bees, the trees nearby and whether you scrape frames or use a propolis trap. Managed colonies tend to collect less resin than wild ones, partly because beekeepers have long favored bees that are easy to work, and smooth Langstroth boxes give them little reason to coat the walls.

Can I sell propolis from my hives?

Possibly, but check your state first. Raw propolis, tinctures and capsules are not covered the same way as honey, and many state cottage food laws are written for low-risk foods only. Anything sold as a dietary supplement falls under federal supplement rules, including manufacturing practices. Ask your state department of agriculture or health, and never claim propolis treats or prevents an illness.

Sources

1. Propolis and bee health: the natural history and significance of resin use by honey bees (Apidologie, 2010), Michael Simone-Finstrom and Marla Spivak, Apidologie
2. Seasonal benefits of a natural propolis envelope to honey bee immunity and colony health (Journal of Experimental Biology, 2015), Renata Borba, Karen Klyczek, Kim Mogen and Marla Spivak, University of Minnesota
3. Thinking inside the box: Restoring the propolis envelope facilitates honey bee social immunity (PLOS ONE, 2024), Maggie Shanahan, Michael Simone-Finstrom, Marla Spivak et al., PLOS ONE (PMC)
4. Renowned Entomologist Delivers Department Seminar on Honey Bee Health (April 2024), Department of Applied Ecology, NC State University
5. Scientific note: often quoted, but not factual data about propolis composition (Apidologie, 2021), Antonio Salatino and Maria Luiza Faria Salatino, Apidologie (Springer)
6. Propolis: a new frontier for wound healing? (Burns & Trauma, 2015), Simona Martinotti and Elia Ranzato, Burns & Trauma
7. Mechanism of action, efficacy, and safety of propolis for the management of oral mucositis: a systematic review (2022), Anis Nur Ramdhiani, Wahyu Hidayat and Indah Suasani Wahyuni, International Journal of Applied Pharmaceutics
8. Nursing Procedures for the Prevention and Treatment of Mucositis Induced by Cancer Therapies: Clinical Practice Guideline (2021), Diana Steinmann et al., Integrative Cancer Therapies
9. Information for Consumers on Using Dietary Supplements, U.S. Food and Drug Administration
10. 21 U.S. Code § 321(ff): definition of dietary supplement, Legal Information Institute, Cornell Law School
11. Label Claims for Food & Dietary Supplements, U.S. Food and Drug Administration
12. 21 CFR § 101.93: Certain types of statements for dietary supplements, Legal Information Institute, Cornell Law School
13. Letter to the Dietary Supplement Industry on the DSHEA Disclaimer (December 11, 2025), U.S. Food and Drug Administration
14. Warning Letter: Beepothecary LLC (October 23, 2020), U.S. Food and Drug Administration and Federal Trade Commission
15. How to Report a Non-Emergency, U.S. Food and Drug Administration
16. Comparison Between Brazilian Propolis and Chinese Propolis: Results From the North American Contact Dermatitis Group 2019-2022 (Dermatitis, 2026), Joel DeKoven et al., Dermatitis (via Duke Scholars)
17. Patch Testing with Propolis of Different Geographical Origins in a Baseline Series (Acta Dermato-Venereologica, 2021), Gunnar Nyman et al., Acta Dermato-Venereologica