How Does Manuka Honey Kill Bacteria? The Science Behind MGO

"Antibacterial" appears on honey labels far more often than it deserves. Most honey has some antibacterial effect, but it is mild and fades quickly. Manuka honey is different, and the reason is chemistry.

The compound at the centre of it is methylglyoxal, better known as MGO. But MGO doesn't work alone. This post explains exactly how manuka honey kills bacteria, why bacteria haven't been able to develop resistance to it, and what the MGO number on the label actually tells you.

Key Takeaways

• Biosota's Australian Manuka honey is independently lab-tested from MGO 150 to MGO 2200+. The higher the MGO, the more the honey can damage and disable the proteins bacteria need to survive ^[1].
• Four things work at the same time: MGO, the high sugar content pulling water out of bacterial cells, the honey's natural acidity, and a compound called hydrogen peroxide. Each targets a different part of the bacterial cell ^{[1, 3, 4]}.
• No bacterial strain has ever developed resistance to manuka honey, across decades of use and deliberate laboratory resistance trials ^{[5, 6]}.

What Makes Manuka Honey Different From Regular Honey?

Most honey has some ability to slow bacteria. The main reason is a natural compound called hydrogen peroxide, which bees produce during hive processing. As bees turn nectar into honey, they release this compound slowly at low levels, enough to slow bacterial growth without damaging skin or tissue ^{[1, 4]}.

Manuka honey does this too. But it also has a second system working independently of the first.

To find it, researchers used a substance that destroys hydrogen peroxide. When they added it to most honeys, the antibacterial effect dropped sharply. When they added it to manuka honey, the antibacterial effect barely changed ^[4]. Something other than hydrogen peroxide is responsible for most of manuka's potency. That something is MGO.

Manuka honey contains far more MGO than any other honey type. Standard honeys typically contain just 1.6 to 24 mg/kg ^[1]. Biosota's Australian Manuka honey is independently lab-tested from MGO 150 to MGO 2200+. That difference explains why manuka honey works where other honeys fall short.

How MGO Attacks Bacteria

MGO is not added to manuka honey. It forms naturally during maturation. The trees that produce manuka honey, known as Leptospermum, contain a natural compound in their nectar that slowly converts into MGO as the honey matures ^[1].

Australia is home to over 80 native Leptospermum species. Some of our highest-medicinal varieties, including Leptospermum liversidgei, Leptospermum Whitei, and Leptospermum Polygalifolium, are found nowhere else in the world. The more of this compound in the source flower, the more MGO in the finished honey.

Once MGO reaches a bacterial cell, it bonds to specific building blocks inside the cell's proteins and locks them in a fixed, inactive position ^[1]. Proteins are the tools bacteria use to grow, divide, build their outer walls, and process nutrients. When enough proteins are disabled, the cell stops working and dies.

The way this happens depends on the bacteria. Against Staphylococcus aureus, the bacteria behind many skin and wound infections, MGO stops cell division mid-cycle. The cell begins to split but cannot complete the process ^[1]. Against Pseudomonas aeruginosa, common in wound and lung infections, MGO damages a key protective protein in the bacterial outer wall, causing the wall to break down and the cell to die ^[1].

Research also confirms that whole manuka honey produces more bacterial cell damage than purified MGO alone ^[2]. The complete honey, not just its MGO content, drives the full antibacterial effect.

Bacterial genetics also confirms this. Bacteria that lack the natural enzyme used to neutralise MGO are significantly more vulnerable to manuka honey, showing that MGO's role in the killing process is central, not incidental ^[2].

The Supporting Mechanisms: Osmosis, Low pH, and Hydrogen Peroxide

MGO is the primary driver. The rest of the honey matrix works alongside it.

Honey is roughly 80% sugars, which creates a very high-sugar, low-water environment. When bacteria come into contact with it, the high sugar concentration pulls water out of the bacterial cell. Without that water, the cell can't function and dies ^[1]. All honeys share this property, but in manuka honey it works alongside MGO rather than being the main event.

Manuka honey is also naturally acidic, with a pH level between 3.2 and 4.5 ^[3]. To put that in context, most disease-causing bacteria grow best in near-neutral conditions. At manuka honey's level of acidity, the internal workings of most bacteria break down: nutrient processing slows, and the cell's ability to maintain normal function is compromised.

Hydrogen peroxide adds a third layer. It is a secondary factor in manuka honey, as the earlier experiments confirm, but it still plays a real role in the overall effect ^[4].

The result is four distinct mechanisms acting at once. Each targets a different part of the bacterial cell. There is no single weak point for bacteria to adapt around.

Why Bacteria Cannot Develop Resistance to Manuka Honey

Most antibiotics work by targeting one specific part of a bacterial cell: one enzyme, one cell wall protein, or one internal process. Bacteria develop resistance by changing that one target. It is a manageable evolutionary adaptation.

Manuka honey doesn't give bacteria that opening. To become resistant, a bacterium would need to change how its proteins function, how its cell wall is constructed, how it divides, and how it removes MGO from its interior, all at once ^[4]. That level of simultaneous, coordinated change across multiple systems has not been observed.

The evidence backs this up. A 2020 review of clinical studies found that bacteria already resistant to multiple antibiotics showed the same vulnerability to manuka honey as bacteria with no antibiotic resistance at all ^[5]. Being resistant to antibiotics provided no advantage against manuka honey. A separate study confirmed that resistance to manuka honey's killing effects has never been documented ^[2]. Researchers have also deliberately tried to force resistance by exposing bacteria to low honey concentrations over many generations. No resistant bacteria emerged from these experiments ^[6].

For clinical detail on how this applies to MRSA, C. difficile, and antibiotic-resistant wound infections, see Antibiotic Benefits of Manuka Honey for Antibiotic-Resistant Infections.

Does Higher MGO Mean Stronger Antibacterial Activity?

For most bacteria, yes. But there is one notable exception.

Researchers measured how closely MGO concentration predicts antibacterial strength across different species. For E. coli the link is strong (r = -0.87). For Enterococcus faecalis it is stronger still (r = -0.94). For Staphylococcus aureus it is moderate (r = -0.54). For Pseudomonas aeruginosa there is no meaningful link ^[7].

The concentration needed to stop bacterial growth confirms this. Purified MGO requires 128 mg/L to stop S. aureus and E. coli from growing. To stop P. aeruginosa, it requires 512 mg/L, four times as much ^[7]. Adding up to 1,000 mg/kg of extra MGO to standard honey and testing it against P. aeruginosa barely shifted the result ^[8].

For P. aeruginosa, the MGO number on the label is not the key factor. It's the full honey matrix that matters.

For most other bacteria of clinical relevance, higher MGO does predict greater antibacterial potency. Natural compounds in whole honey also contribute, and whole honey consistently outperforms purified MGO at the same concentration ^[4].

What the Latest Research Shows (2023-2026)

The science of how manuka honey works continues to develop.

A 2023 study published in Frontiers in Cellular and Infection Microbiology tested manuka honey combined with conventional antibiotics against three Staphylococcus species. In most tested combinations, the honey made the antibiotics more effective than either agent achieved alone ^[9].

A 2024 review in AIMS Microbiology confirmed that manuka honey's antibacterial power comes from multiple factors working together, including natural plant compounds in the honey and its MGO concentration ^[10]. A separate compound, called leptosperin, is found only in Leptospermum honeys and serves as a natural marker of genuine manuka honey. Early research suggests it may also contribute to antibacterial and anti-inflammatory effects alongside MGO ^[1].

One emerging line of research suggests MGO may also interact with the body's immune system. Early evidence indicates that MGO-modified compounds in the honey may activate a group of specialised immune cells in the skin and mucous membranes, adding an immune dimension to manuka's antibacterial properties. The primary research study had not been independently confirmed at the time of writing; this is an area to watch, not a settled finding ^[11].

Explore the full range of Biosota Manuka honey's health benefits, from gut health and immunity to wound care and skin support.

FAQ: Common Questions About Manuka Honey and Bacteria

Does manuka honey kill all bacteria?

Manuka honey works against a wide range of bacteria, including Staphylococcus aureus, E. coli, and E. faecalis. Some bacteria, particularly Pseudomonas aeruginosa, respond less strongly to MGO. For these species, the full honey matrix, including its sugar content, acidity, and natural plant compounds, matters more than the MGO grade alone ^{[7, 8]}.

What MGO level do I need for antibacterial effects?

MGO 250+ mg/kg is the commonly cited level for reliable antibacterial potency in wound and oral care applications ^[12]. For skin infections and more demanding use cases, MGO 1200+ is recommended. See Manuka Honey for Wounds and Ulcers for practical guidance.

Can I use manuka honey instead of antibiotics?

No. Manuka honey is not a substitute for prescribed antibiotics. Research shows it can enhance how antibiotics perform when used alongside them ^[9], making it a complement rather than a replacement. Always consult a healthcare professional before changing any treatment plan.

Is the antibacterial effect destroyed by heat?

MGO is more heat-stable than hydrogen peroxide. Its antibacterial activity stays intact after heat treatments that would destroy other honey compounds ^[1]. Biosota Manuka honey is cold-extracted and never heat-treated. See also Antibacterial Benefits of Manuka Honey for Skin Infections for topical guidance.

References

1. Roberts et al., "On the Antibacterial Effects of Manuka Honey: Mechanistic Insights", Cardiff University: https://orca.cardiff.ac.uk/id/eprint/134665/1/RRB-75754-on-the-antibacterial-effects-of-manuka-honey--mechanistic-in_102915%20(1).pdf
2. Pettit et al., "Manuka Honey Has Broad-Spectrum Antimicrobial Activity", mSystems 2020: https://journals.asm.org/doi/10.1128/msystems.00106-20
3. Antibacterial mechanisms and pH study, PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0224495
4. Maddocks et al., "Antibacterial Activity of Manuka Honey and Its Components", PMC 2018: https://pmc.ncbi.nlm.nih.gov/articles/PMC6613335/
5. Nolan et al., Systematic review of MDR susceptibility to honey, PMC 2020: https://pmc.ncbi.nlm.nih.gov/articles/PMC7693943/
6. Johnston et al., "Therapeutic Review of Manuka Honey", Frontiers in Microbiology 2016: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00569/full
7. Sherburn et al., "MGO-Activity Correlation and MIC Data", PLOS ONE 2022: https://pmc.ncbi.nlm.nih.gov/articles/PMC9333225/
8. Sherburn et al., "MGO Supplementation Experiment", PLOS ONE 2022: https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0272376
9. Alkathiri et al., "Manuka Honey Combined With Antibiotics", Frontiers in Cellular and Infection Microbiology 2023: https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1219984/full
10. "Manuka Honey Antibacterial Activity: Multi-Component Review", AIMS Microbiology 2024: https://www.aimspress.com/article/doi/10.3934/microbiol.2024015?viewType=HTML
11. Malaghan Institute, "MAIT Cells and Manuka Honey" (summarises Food & Function study; primary paper not independently confirmed): https://www.malaghan.org.nz/news-and-resources/news/mait-cells-and-manuka-honey-scientists-uncover-novel-antibacterial-mechanism
12. Australia's Manuka, MGO Threshold Reference: https://www.australiasmanuka.com.au/mgo-manuka-honey/