Propolis: what it is, what the evidence shows, allergy risks and UK rules

Propolis is a sticky resin that honey bees collect from tree buds, mostly poplars in Britain, and mix with wax to seal and line the inside of their hive. In the laboratory its extracts kill or slow many bacteria and fungi, but good clinical evidence in people is thin: no health claim for propolis is authorised in the UK, and it is a well documented cause of contact allergy. This guide explains what propolis is, what it does for the colony, what the research really supports, the UK rules on supplements and claims, the allergy risks and how beekeepers harvest it cleanly.

What is propolis and why do bees make it?

The name comes from Greek pro, in front of, and polis, the city. Beekeepers call it bee glue, because it welds frames, crown boards and supers together and makes a hive tool essential from the first inspection.

A material that changes with the weather

Propolis is hard and brittle when cold and soft and tacky when warm. Its colour runs from yellow-green to dark brown depending on the trees the bees visited, and it has a strong resinous smell. Placed in alcohol it separates into an insoluble waxy part and a dissolved fraction, the “balsam”, which carries most of the compounds researchers study and forms the basis of commercial tinctures.

How the colony uses it

The standard review on the subject, by Michael Simone-Finstrom and Marla Spivak in Apidologie (2010), describes several jobs propolis does in the nest:

• Sealing gaps and narrowing entrances. Bees fill cracks, reduce the entrance and smooth the surfaces where comb is attached. In a National or WBC hive, any gap narrower than bee space ends up glued.
• Building a propolis envelope. A wild colony studied in a hollow tree had lined its cavity walls with a thin layer, 0.3 to 0.5 mm thick.
• Embalming intruders. A dead mouse or large insect too heavy to drag out is 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 stop it breeding. The beetle is not established in the UK and is a notifiable pest, so British beekeepers will not see this behaviour at home.

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

Part of the colony’s social immunity

Researchers describe propolis as part of social immunity, the colony’s collective defence against disease. Simone-Finstrom and Spivak report that after seven days, young bees in colonies whose walls had been coated with propolis expressed two immune-related genes at lower levels, which suggests a lower microbial load in the nest.

A University of Minnesota field study led by Renata Borba and 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 autumn, with no difference in measured pathogen or parasite levels. In one of the two winters, colonies with an envelope came out stronger and with higher vitellogenin levels. A 2024 follow-up by Spivak’s group in PLOS ONE found that boxes with roughened inner walls gathered the most propolis, that the European foulbrood bacterium was detected significantly less in rough-box colonies on migratory operations, and that varroa showed only a non-significant downward trend. Survival did not differ.

In laboratory tests, propolis extracts inhibit Paenibacillus larvae, the bacterium behind American foulbrood, and in a Petri dish a 10% ethanol extract killed all the varroa mites tested. The 2010 review is careful to add 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 for foulbrood: in the UK only veterinary medicines authorised by the Veterinary Medicines Directorate may be used against varroa, and American and European foulbrood are notifiable diseases that must be reported to the bee health authorities.

How do honey bees collect resin?

The trees British bees visit

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

The work of resin foragers

Only a small share of foragers collect resin, and they appear to specialise, 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 home she cannot unload alone. Other workers pull the resin from her baskets, usually in around fifteen minutes, but it can take one to seven hours or even overnight.
5. Those workers mix 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 10:00 and 15:30, when warmth makes resin workable, and it is reported to peak from late summer into autumn as nectar flows fade. In Britain that means August and September, after the summer flow and, on the moors, around the heather.

The chemistry comes from the tree

Propolis chemistry largely mirrors the resin it came from, although some volatile compounds evaporate on the way home. This is the key to everything that follows: poplar propolis from a Hampshire 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 quote the same composition: about 50% plant resins and balsams, 30% wax, 10% essential and aromatic oils, 5% pollen and 5% other matter. It even appears 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 these figures back through decades of copying 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 Brazilian quality standards as an example of real benchmarks: at most 25% wax, 5% ash and 8% moisture, and at least 5% phenolic compounds and 0.5% flavonoids. 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 favourite of laboratory researchers.
• 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 consequence: a study on one propolis tells you little about the next unless its chemistry has been analysed.

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

Martinotti and Ranzato group propolis by origin. In summary:

Type	Where	Main plant source	Marker compounds
Poplar (brown) propolis	Europe including the UK, North America	poplar buds, sometimes conifers	flavonoids and other polyphenols
Green propolis	south-east 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 green propolis better?

Green propolis is often sold at a premium and presented 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 researched 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.

Brown poplar propolis, the kind British colonies produce, is the most studied type in Europe. If you want a home-grown product, look for the country 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 laboratory

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

Wounds and skin: mostly animal data

Propolis turns 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 is mainly laboratory and rodent work. The authors list the gaps themselves: many studies never characterise the propolis tested, and bioavailability, product stability and safe, effective doses are not 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 authority has adopted it as a reference dose.

Mouth ulcers from cancer treatment: promising but unconfirmed

The best documented human use is oral mucositis, the painful mouth inflammation caused by chemotherapy and radiotherapy. 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 only covered English-language papers from 2016 to 2021 and mixed animal studies with small trials. A 2021 practice guideline from German-speaking cancer centres, 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 the oncology team, never self-treatment.

What has not been shown

Boosting immunity, preventing colds, protecting the liver, heart or gut, acting as a “natural antibiotic”: none of these has been backed by trials strong enough to persuade regulators. If a propolis supplement says it “contributes to the normal function of the immune system”, check the ingredients. That wording is an authorised claim for vitamin C, zinc and a few other nutrients, and it will be there because of what has been added, not because of the propolis.

Does propolis help a sore throat?

Throat sprays, lozenges and pastilles are the most common propolis products on British shelves. An honest summary:

• No throat or respiratory claim is authorised. EFSA examined the claims put forward for propolis in 2010, including respiratory health, throat comfort and oral health, and accepted none.
• Most sore throats are viral and get better on their own within about a week. Anything taken during that time tends to look as if it worked.
• Products usually mix several ingredients, such as honey, essential oils, plant extracts and vitamin C, so any effect cannot be pinned on the propolis.
• Honey and sugar soothe 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 problems. Speak to a pharmacist, use NHS 111 or see your GP if you have a high temperature, difficulty swallowing or breathing, swollen painful glands, or symptoms that are not improving. Some bacterial throat infections need antibiotics, and only a prescriber can decide that.

What are the UK rules on propolis supplements and claims?

Propolis is sold as a food or food supplement

Capsules, tablets and liquid extracts of propolis sold in dose form are food supplements. In Great Britain and Northern Ireland they fall under parallel regulations made in 2003: the Food Supplements (England) Regulations 2003, the Food Supplements (Scotland) Regulations 2003, the Food Supplements (Wales) Regulations 2003 and the Food Supplements (Northern Ireland) Regulations 2003. Government guidance on these rules confirms that they cover any “other substance with a nutritional or physiological effect”, not just vitamins and minerals, and that every food supplement label must give:

• the recommended daily portion, for example the number of capsules;
• a warning not to exceed it;
• a statement that supplements should not replace a varied diet;
• advice to keep the product out of reach of young children.

Food supplements do not need approval before sale. Enforcement is the job of local authority trading standards and environmental health officers.

No authorised health claim for propolis

Health claims on food are governed by Regulation (EC) No 1924/2006, which Great Britain kept after Brexit in an amended form. Since 1 January 2021, a health claim may be used in England, Scotland and Wales only if it is authorised and listed on the GB Nutrition and Health Claims Register, kept by the Department of Health and Social Care, and the product meets its conditions of use. The register also lists rejected claims with the reasons.

The claims put forward for propolis were assessed by EFSA’s expert panel in 2010, before Brexit. They covered respiratory health, throat comfort, gut health, immunity, oral health, circulation, liver protection and antibacterial and antifungal activity. The panel noted that the references showed different biological activity depending on the origin of the propolis, that the supposed active ingredients were sometimes present in tiny or undetectable amounts, and that it was not even clear which preparation the claims referred to. In short, it was not clear which type of propolis preparation or constituent the claims were made for, so none was authorised, and no propolis claim has been added to the GB register since. In 2017 the Advertising Standards Authority upheld complaints against a UK propolis seller whose ads called it “antibacterial” and “for the immune system”, noting that no health claim for propolis was authorised.

Government guidance adds two points that matter for propolis:

• Vague claims count. Statements such as “good for you” are general health claims and must be accompanied by a specific authorised claim.
• Disease claims are banned on food. Saying that a food prevents, treats or cures a human disease is not permitted, whatever the evidence.

Northern Ireland follows EU rules

Under the Windsor Framework, EU food law, including Regulation 1924/2006 itself, continues to apply directly in Northern Ireland, and claims for the Northern Ireland market go through the European Commission’s register rather than the GB one. For propolis the outcome is the same, since no claim is authorised in either register, but a Northern Ireland business should check the EU rules, and the Food Standards Agency is the competent authority there.

When propolis becomes a medicine

The MHRA decides where food ends and medicine begins. Its Guidance Note 8 explains that a product is a medicine if it is presented as treating or preventing disease, whatever it contains, or if it acts on the body through a pharmacological, immunological or metabolic action. The agency looks at everything: the name, the label, the website, social media posts and customer testimonials. Wording such as “protects against” or “may help with” a condition can make a product a medicine by presentation, and a medicine needs a licence or, for herbal medicines, a Traditional Herbal Registration. A jar of propolis tincture sold as a “natural antibiotic” or a “cold remedy” is therefore an unlicensed medicine in the eyes of the MHRA.

Propolis side effects, allergy and who should avoid it

Contact allergy is the main risk

Propolis is one of the best documented natural contact allergens. In February 2020 the British Association of Dermatologists publicised a UK study showing that the share of patch-tested patients reacting to propolis rose from 2.35% in 2007 to 2010 to 3.94% in 2015 to 2018, an increase of 68%. The association pointed out that propolis is not routinely included in UK patch testing, so some allergic patients may go unidentified, and that “natural” products are not necessarily safer.

A study of 1,470 patients with dermatitis 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. Because propolis varies so much, a negative test with one sample does not fully rule out allergy.

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

Cross-reactions with balsam of Peru, colophony and fragrance

Propolis shares several allergens with balsam of Peru (Myroxylon pereirae), a resin used in fragrance and flavouring. The 2021 study found co-reactions to balsam of Peru, colophony (pine rosin, found in sticking plasters, adhesives and some varnishes) or fragrance mixes in 12.5% to 50% of propolis-allergic patients. If you already 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 swelling of the throat or widespread eczema in someone already sensitised. Severe immediate allergic reactions are rare, but they have been reported. Seek emergency help by calling 999 if lips, tongue or throat swell, or if breathing becomes difficult.

Who should avoid propolis?

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

Testing, diagnosis and reporting a reaction

Before using a propolis cream or balm, try 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 proper patch testing. The NHS explains that a GP will usually diagnose contact dermatitis from the appearance of the skin and your history, and may refer you to a dermatologist if the trigger is unclear. Patch tests are applied to the back, removed at day 2 and read again at day 4, because allergic reactions can take that long to show. Ask specifically for propolis to be included if you have used bee products.

The MHRA Yellow Card scheme covers medicines and herbal or complementary products, but food supplements are not on its list. Tell your GP or pharmacist about a reaction, and report an unsafe or mislabelled product to your council’s trading standards or environmental health team.

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 (glycerine or water)	adults avoiding alcohol	strength often lower and rarely stated
Throat spray	mouth and throat	usually combined with other ingredients
Lozenges and pastilles	throat	sugar or sweeteners
Capsules and tablets	food supplement	check whether the stated milligrams are extract or raw propolis
Raw propolis	chewing, or making an extract	dose impossible to know; possible debris
Creams, balms, cosmetics	skin and lips	contact allergy risk

Reading the label

A well labelled product should tell you:

1. Where the propolis came from, or at least the country, since origin determines chemistry.
2. How much propolis or extract is in each dose, and ideally its phenolic or flavonoid content. Be wary of headline figures such as “1000 mg” that do not say whether they refer to extract or to the raw propolis it was made from.
3. The full ingredients list, so you can spot alcohol, sugars, essential oils and added vitamins.
4. An allergy warning for people sensitive to bee products.
5. The mandatory food supplement statements: daily dose, do not exceed, not a substitute for a varied diet, keep out of reach of children.
6. A batch number and best before date.

Be sceptical of cure claims, “immune booster” wording attributed to propolis alone and online-only products with no identifiable UK or EU business behind them. The same habits apply to honey, as explained in our guide on how to choose honey.

How long to take it

No health authority has set a reference dose for propolis. Follow the label, do not exceed it, and avoid taking propolis products continuously or repeatedly through the year without advice from 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?

Clean propolis, free of wood splinters, paint flakes and treatment residues, takes a little planning.

Scraping or a propolis mat

Scraping means collecting with the hive tool the propolis on top bars, frame runners and the upper walls of the brood box during inspections. It tends to be mixed with wax, wood, bee parts and, on painted or treated hives, paint or preservative. Keep scrapings for your own use or for melting.

A propolis mat or screen uses 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 crown board or directly beneath it. The bees fill the slots to block light and draughts, and the result is much cleaner propolis that pops out easily once frozen.

Harvesting with a mat, step by step

1. Fit the mat on strong, healthy colonies after the main summer flow, typically from late July to September depending on your area. Colonies propolise most as autumn approaches.
2. Let in a little light or air above the mat, for example by lifting one corner of the crown board slightly or removing insulation, to encourage sealing.
3. Remove the mat once the slots are well filled, usually after several weeks, and before you put the colony to bed for winter so it is not left under a poorly insulated ceiling.
4. Freeze the mat for a few hours in a clean bag so the propolis becomes hard and brittle.
5. Flex and tap the mat while it is still cold over a clean tray; the propolis breaks away in flakes.
6. Pick out debris and store the flakes in a closed glass jar or food bag, away from light, heat and damp.

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

Quality and safety points

• Do not collect during varroa treatment. Some acaricides, especially fat-soluble ones, build up in wax and can pass into propolis. Take mats off before any treatment, and only refit them once the treatment is complete and strips have been removed, following the product’s summary of product characteristics. In much of England and Wales, late summer treatment and the propolis window overlap, so you may have to choose one or fit mats only to colonies you treated earlier.
• Never scrape painted or preservative-treated woodwork, and keep propolis from second-hand boxes of unknown history out of anything you sell.
• Clean and store mats after use where wax moth cannot reach them.
• Protect your hands. Many beekeepers become sensitised to propolis over the years. Nitrile gloves reduce exposure when scraping or cracking mats.

Selling propolis: what the law allows

You can sell raw propolis or an extract as a food or food supplement. Register as a food business with your local council at least 28 days before you start, label it correctly, and include an allergy warning for people sensitive to bee products. You may describe where and how it was collected, the trees in the area and its smell and colour. You may not attribute any preventive or curative property to it: phrases such as “heals sore throats” or “natural antibiotic” are banned on food, and presenting propolis that way would turn it into a medicine requiring MHRA authorisation. If you sell in Northern Ireland, check the EU-derived rules that apply there. For organising your honey room and batch records, see our guide to harvesting honey.

Frequently asked questions

Does propolis work for a sore throat?

There is no good evidence that it does. The European Food Safety Authority assessed the throat, respiratory and oral health claims put forward for propolis in 2010 and accepted none, so no such claim is authorised on the GB register. Most sore throats are viral and clear within a week. See a pharmacist or GP if you have a high temperature, trouble swallowing or breathing, or symptoms that keep getting worse.

Who should not take propolis?

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

Is propolis a natural antibiotic?

Not in any medical sense. Propolis extracts slow the growth of some bacteria and fungi in laboratory dishes, but activity varies widely with where the propolis came from, and no robust clinical trial shows it can treat an infection. It never replaces an antibiotic your GP has prescribed, and selling it as an antibiotic would make it an unlicensed medicine under UK law.

Is propolis allergy common in the UK?

It is one of the better known contact allergens. A study publicised by the British Association of Dermatologists in 2020 found the share of UK patients reacting to propolis rose from 2.35% in 2007 to 2010 to 3.94% in 2015 to 2018. Because propolis is not routinely included in UK patch testing, some cases are probably missed. Beekeepers are among the most exposed.

What is green propolis?

Green propolis comes from south-east Brazil, where bees collect resin from the shrub Baccharis dracunculifolia. It is low in wax and rich in artepillin C, a compound absent from the poplar propolis British bees make. It is not proven to be better for health, only chemically different, so research on one type cannot simply be applied to the other.

How much propolis does one hive produce?

Usually a few tens of grams to a few hundred grams a year, depending on the bees, the trees nearby and whether you scrape frames or use a propolis mat. Many British colonies propolise far less than wild colonies, partly because beekeepers have long selected bees that are easy to open. Treat any figure as a rough range rather than a target.

Can I sell propolis from my hives?

Yes, as a food or food supplement, provided you are registered with your local council as a food business and follow labelling rules. You may describe where and how it was collected and what it tastes like, but you may not say it prevents, treats or cures anything. A product presented that way becomes a medicine in the eyes of the MHRA and needs a licence.

How do I get propolis off my hands?

Propolis does not wash off with water. Rub your hands with a little vegetable oil or a waterless hand cleaner, then wash with soap. Surgical spirit also works but dries the skin. The better habit is to wear nitrile gloves when scraping frames or cracking mats, because repeated skin contact is how many beekeepers become sensitised over the years.

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. Scientific note: often quoted, but not factual data about propolis composition (Apidologie, 2021), Antonio Salatino and Maria Luiza Faria Salatino, Apidologie (Springer)
5. Propolis: a new frontier for wound healing? (Burns & Trauma, 2015), Simona Martinotti and Elia Ranzato, Burns & Trauma
6. 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
7. Nursing Procedures for the Prevention and Treatment of Mucositis Induced by Cancer Therapies: Clinical Practice Guideline (2021), Diana Steinmann et al., Integrative Cancer Therapies
8. Scientific Opinion on the substantiation of health claims related to propolis and flavonoids in propolis (EFSA Journal 2010; 8(10):1810), European Food Safety Authority, NDA Panel
9. Great Britain nutrition and health claims (NHC) register, Department of Health and Social Care, GOV.UK
10. Nutrition and health claims: guidance to compliance with Regulation (EC) 1924/2006, Department of Health and Social Care, GOV.UK
11. Regulation (EC) No 1924/2006, Article 20: Register (as it applies in Great Britain), legislation.gov.uk
12. ASA Ruling on Medibee Ltd (4 January 2017), Advertising Standards Authority
13. Guidance notes on legislation implementing Directive 2002/46/EC on food supplements, Department of Health and Social Care, GOV.UK
14. Guidance Note 8: A guide to what is a medicinal product, Medicines and Healthcare products Regulatory Agency (MHRA)
15. Yellow Card: what you can report, MHRA
16. Contact dermatitis: diagnosis, NHS
17. Study finds rise in allergy to natural skincare ingredient (28 February 2020), British Association of Dermatologists, Skin Health Info
18. Patch Testing with Propolis of Different Geographical Origins in a Baseline Series (Acta Dermato-Venereologica, 2021), Gunnar Nyman et al., Acta Dermato-Venereologica