Manuka

What Is Manuka?

Manuka (Leptospermum scoparium) is a hardy shrub or small tree in the myrtle family (Myrtaceae), native to New Zealand and southeast Australia. It is held in high regard in Māori medicine, where the leaves, bark and gum were used as traditional remedies. The plant yields two quite different medicines that are easy to conflate: a steam-distilled leaf essential oil and manuka honey, which bees make from its nectar but which carries a different active chemistry.

Manuka is best known worldwide through the honey, graded by its non-peroxide antibacterial strength (the Unique Manuka Factor, UMF) — an activity that comes from methylglyoxal in the honey, not from the plant tissue ^{11,25Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →Reference 25Mavric et al. · 2008Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New ZealandView study →}. The leaf oil is a separate story: its antibacterial, antifungal and antiviral activity is real but almost entirely in vitro, strongest against Gram-positive bacteria, and traces to a fraction of β-triketones (chiefly leptospermone) ^{1,4Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 4Christoph et al. · 2000In vitroA comparative study of the in vitro antimicrobial activity of tea tree oils with special reference to the activity of β-triketones [in vitro]View study →}.

A defining caveat runs through the oil literature: manuka oil is extraordinarily chemotype-dependent. The amount of triketone varies enormously with where the plant was grown, so a result from a high-triketone East Cape oil does not transfer to a sesquiterpene-rich South Island oil — and neither transfers to the honey ^{2,3Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}.

A common myth, corrected. Manuka is sometimes described as the “female” and kānuka the “male” of one tree. That is botanically wrong: manuka (Leptospermum scoparium) and kānuka (Kunzea ericoides) are two different species in two different genera, distinguished in the field by feel — manuka leaves are prickly, kānuka soft.

Traditional & Modern Uses

In Māori and Western folk practice manuka has been used both internally and topically. Internally, leaf infusions and decoctions were taken for gastrointestinal complaints (diarrhoea, colic, dysentery), urinary conditions, fevers and colds — uses that rest on traditional and textbook documentation rather than clinical trials. Topically and as a vapour, the leaf and oil were applied for wounds, skin infections and inflammation, and gargled for oral hygiene. These are best read as ethnobotanical uses, not evidence-based indications.

The modern evidence sits mostly with manuka honey as a topical agent. Medical-grade honey dressings have been trialled for wound care and burns, with modest and uncertain benefit ^{9,10Reference 9Jull et al. · 2015Systematic reviewHoney as a topical treatment for wounds [systematic review]View study →Reference 10Norman et al. · 2017Systematic reviewAntiseptics for burns [systematic review]View study →}, and the honey has been tested — largely without success — for radiation-induced oral mucositis ^{14,15Reference 14Bardy et al. · 2012RCTA double-blind, placebo-controlled, randomised trial of active manuka honey and standard oral care for radiation-induced oral mucositis [randomised controlled trial]View study →Reference 15Hawley et al. · 2014RCTA randomized placebo-controlled trial of manuka honey for radiation-induced oral mucositis [randomised controlled trial]View study →} and, more encouragingly, for plaque and gingivitis ^{16Reference 16English et al. · 2004RCTThe effects of manuka honey on plaque and gingivitis: a pilot study [randomised controlled trial]View study →}. The essential oil, by contrast, has no completed human trials; its antibacterial, antifungal, antiviral and antiparasitic activity is documented in vitro and in animal/veterinary models.

Manuka honey is standardised by phenol/methylglyoxal content and expressed as a UMF value. Higher-UMF honeys show stronger in-vitro activity against resistant organisms including MRSA, but this is dose- and strain-dependent laboratory activity, not a guaranteed clinical kill-threshold ^{11Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →}.

Botany & Varieties

Manuka is a member of the Myrtaceae (myrtle) family — a large group of aromatic, essential-oil-rich trees and shrubs that also includes tea tree (Melaleuca alternifolia), eucalyptus, clove and its close New Zealand relative kānuka (Kunzea ericoides). It is an evergreen shrub to small tree with small, prickly leaves and abundant white to pink five-petalled flowers.

The single most practical botanical fact about manuka is its chemotype variation. Steam-distilled oils fall into recognisably different chemical forms depending on provenance ^{2,3Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}:

• East Cape “triketone” chemotype — high in β-triketones (leptospermone and relatives, often 20–33% of the oil); this is the antimicrobially active form.
• Far-north chemotype — rich in pinene, low in triketones.
• South Island chemotype — dominated by sesquiterpene hydrocarbons (up to ~65% of the oil), low in triketones.

Because commercial “manuka oil” can be any of these, antimicrobial performance is not interchangeable between products.

Habitat & Distribution

Manuka is native to New Zealand and southeast Australia (including Tasmania), where it is a common pioneer of scrubland, forest margins and regenerating cleared land. New Zealand is the centre of both wild stands and commercial production, and the plant’s chemotype tracks region — the high-triketone material is associated with the East Cape of the North Island ^{3Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}. It is hardy and adaptable, tolerating poor soils and exposed sites, which is why it colonises disturbed ground readily.

Phytochemistry

Manuka’s medicine is largely an essential-oil story, and that oil is dominated by two fractions ^{1,2,3Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}. The first is a set of cyclic β-triketones — chiefly leptospermone, with isoleptospermone and flavesone — which together account for roughly 20% of the oil (often 20–33% in the prized East Cape “triketone” chemotype) and carry the bulk of its antibacterial and antifungal punch. The second is a heavy load of sesquiterpene hydrocarbons (≥60% of the oil), led by trans-calamenene (mean ~12.5%) alongside cadinene- and copaene-type compounds.

Bioassay-guided fractionation of the foliage has isolated further antibacterial phloroglucinols beyond the classical three — notably the nortriketone grandiflorone ^{5,7Reference 5Killeen et al. · 2016In vitroNortriketones: antimicrobial trimethylated acylphloroglucinols from mānuka (Leptospermum scoparium) [in vitro]View study →Reference 7Xu et al. · 2024In vitroTLC-bioautography-guided isolation and assessment of antibacterial compounds from manuka (Leptospermum scoparium) [in vitro]View study →}. Manuka oil is highly chemotype-dependent: a far-north form is rich in pinene, the East Cape form is high-triketone, and South Island plants run high in sesquiterpenes (up to ~65%). Minor citronellal and astringent tannins round out the leaf.

It is worth separating the oil from the famous honey. Manuka honey is a separate product whose non-peroxide antibacterial activity comes from methylglyoxal (MGO), formed from nectar-derived dihydroxyacetone as the honey matures — graded by the Unique Manuka Factor (UMF) ^{11,25Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →Reference 25Mavric et al. · 2008Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New ZealandView study →}. MGO is a honey constituent, not a constituent of the plant tissue, so it is not tabled below.

Constituent Summary

Figures are share of the steam-distilled essential oil (mass %), pooled from GC studies of New Zealand oils; values vary widely by chemotype and region. Whole-oil yield from the leaf is ~0.2–1%.

Pharmacology & Research

Manuka’s research base splits cleanly into two products that are easy to conflate: the steam-distilled leaf essential oil and manuka honey, which the bees make from the nectar but which carries a different active chemistry. The oil literature is almost entirely preclinical — in vitro assays and a handful of animal or veterinary models showing antibacterial, antifungal, antiviral and acaricidal activity that traces largely to its β-triketones (leptospermone and relatives) ^{1,2,3,4Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →Reference 4Christoph et al. · 2000In vitroA comparative study of the in vitro antimicrobial activity of tea tree oils with special reference to the activity of β-triketones [in vitro]View study →}. The honey, by contrast, is where the human trials sit: several randomised controlled trials and Cochrane reviews cover topical wound care, radiation-induced oral mucositis and gingivitis, with mixed-to-modest results ^{9,10,14Reference 9Jull et al. · 2015Systematic reviewHoney as a topical treatment for wounds [systematic review]View study →Reference 10Norman et al. · 2017Systematic reviewAntiseptics for burns [systematic review]View study →Reference 14Bardy et al. · 2012RCTA double-blind, placebo-controlled, randomised trial of active manuka honey and standard oral care for radiation-induced oral mucositis [randomised controlled trial]View study →}. The single largest caveat runs through everything below — manuka oil is extraordinarily chemotype-dependent, so an antimicrobial result from a high-triketone East Cape oil does not transfer to a sesquiterpene-rich South Island oil, and neither transfers to the honey ^{2,3Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}.

1. Antibacterial

This is the strongest and most-replicated activity, but it belongs to the essential oil, not an internal herb preparation. Across GC-characterised New Zealand oils, antibacterial potency tracks the β-triketone fraction — chiefly leptospermone with isoleptospermone and flavesone — and is consistently strongest against Gram-positive bacteria, including Staphylococcus aureus and MRSA, with weaker activity against Gram-negatives ^{1,2,4Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 4Christoph et al. · 2000In vitroA comparative study of the in vitro antimicrobial activity of tea tree oils with special reference to the activity of β-triketones [in vitro]View study →}. Bioassay-guided fractionation repeatedly isolates the triketones (and the related grandiflorone and other nortriketones) as the active principles ^{5,7Reference 5Killeen et al. · 2016In vitroNortriketones: antimicrobial trimethylated acylphloroglucinols from mānuka (Leptospermum scoparium) [in vitro]View study →Reference 7Xu et al. · 2024In vitroTLC-bioautography-guided isolation and assessment of antibacterial compounds from manuka (Leptospermum scoparium) [in vitro]View study →}, and isolated leptospermone alone shows measurable antibacterial activity ^{6Reference 6Jeong et al. · 2018In vitroAntimicrobial activities of leptospermone isolated from Leptospermum scoparium [in vitro]View study →}. Veterinary work extends this to Gram-negative canine ear pathogens when the oil is paired with a permeabiliser (Tris-EDTA) ^{8Reference 8Song et al. · 2020In vitroIn vitro antibacterial activity of the manuka essential oil from Leptospermum scoparium combined with Tris-EDTA against Gram-negative bacterial isolates from dogs with otitis externa [in vitro]View study →}. Note this is separate from manuka honey’s antibacterial action, which comes from methylglyoxal, not the plant ^{11Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →}.

Gap: every result is in vitro or veterinary — there are no human clinical trials of the oil as an internal or systemic antibacterial, and MICs vary widely with chemotype.

2. Wound healing

The clearest human evidence for anything “manuka” is topical manuka honey in wound care — but this is the honey, a distinct product, not the leaf or oil. A Cochrane review of honey for wounds found it may shorten healing of partial-thickness burns and infected post-operative wounds versus some comparators, while evidence for other wound types was of low certainty ^{9Reference 9Jull et al. · 2015Systematic reviewHoney as a topical treatment for wounds [systematic review]View study →}. A separate Cochrane review of antiseptics for burns likewise found honey among the better-supported options but flagged low-to-moderate certainty overall ^{10Reference 10Norman et al. · 2017Systematic reviewAntiseptics for burns [systematic review]View study →}. A small randomised trial of manuka honey on blepharoplasty (eyelid) wounds found no meaningful cosmetic or healing advantage over petrolatum ^{12Reference 12Malhotra et al. · 2017RCTEffect of manuka honey on eyelid wound healing: a randomized controlled trial [randomised controlled trial]View study →}, illustrating that positive signals are inconsistent. Mechanistically the honey combines osmotic drawing, low pH and methylglyoxal-driven antibacterial action ^{11Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →}.

Gap: the evidence is for medical-grade honey dressings, not the herb; certainty is low, trials are heterogeneous, and null results (e.g. eyelid wounds) exist.

3. Antifungal

The oil shows reproducible in vitro antifungal activity, again chemotype-dependent. Constituent-oriented comparisons of Myrtaceae “tea-tree” oils found manuka oil and its isolated β-triketone complex gave the best inhibition of dermatophytes among the group ^{4Reference 4Christoph et al. · 2000In vitroA comparative study of the in vitro antimicrobial activity of tea tree oils with special reference to the activity of β-triketones [in vitro]View study →}, and isolated leptospermone inhibits fungal growth directly ^{6Reference 6Jeong et al. · 2018In vitroAntimicrobial activities of leptospermone isolated from Leptospermum scoparium [in vitro]View study →}. Reviews collate activity against Candida, Trichophyton and other dermatophytes, though potency is inconsistent across oil samples ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}. Only some chemotypes carry strong antifungal punch — the high-triketone East Cape form is the relevant one ^{3Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}.

Gap: in vitro only; no human antifungal trials, and results are highly sensitive to oil composition.

4. Antiparasitic

An active and fast-growing preclinical frontier. The β-triketones are HPPD inhibitors, and this maps onto parasiticidal effects: manuka oil and isolated β-triketones show miticidal and ovicidal activity against the scabies mite Sarcoptes scabiei in vitro, positioning them as candidate scabicides ^{19,20Reference 19Nammunige et al. · 2025In vitroNammunige, N. A., Agnew-Francis, K. A., Fernando, D. D., et al. (2025). β-Triketones from Leptospermum scoparium (mānuka) oil show potential as scabicides [in vitro]. Phytomedicine. https://pubmed.ncbi.nlm.nih.gov/39752786/View study →Reference 20Taylor et al. · 2022In vitroInvestigating the antibacterial properties of prospective scabicides [in vitro]View study →}. Triketone analogues derived from the oil are acaricidal against house-dust and stored-food mites, out-performing benchmark agents in some assays ^{21Reference 21Jeong et al. · 2009In vitroAcaricidal activity of triketone analogues derived from Leptospermum scoparium oil against house-dust and stored-food mites [in vitro]View study →}, and whole-oil fractions kill cattle-tick (Rhipicephalus microplus) larvae and adults ^{22Reference 22Duque et al. · 2021In vitroAcaricidal activity of the essential oils from Leptospermum scoparium, Origanum vulgare and Litsea cubeba on Rhipicephalus microplus [in vitro]View study →}. The same leptospermone chemistry drives insecticidal activity against Aedes aegypti mosquitoes via rapid knockdown ^{23Reference 23McComic et al. · 2025AnimalMode of toxicity of the β-triketone leptospermone to Aedes aegypti mosquitoes [animal model]View study →}.

Gap: entirely in vitro/ex vivo or arthropod-model work — no clinical scabies or ectoparasite trials in humans yet, though the scabicide programme is the most likely to reach one.

5. Oral mucositis

Manuka honey has been tested for radiation-induced oral mucositis in head-and-neck cancer, and the better-powered trials are largely negative. A double-blind placebo-controlled RCT (n=131) of active manuka honey versus standard oral care found no significant reduction in mucositis severity ^{14Reference 14Bardy et al. · 2012RCTA double-blind, placebo-controlled, randomised trial of active manuka honey and standard oral care for radiation-induced oral mucositis [randomised controlled trial]View study →}, and a subsequent randomised placebo-controlled trial reached similar null conclusions, partly limited by poor tolerability of the honey during radiotherapy ^{15Reference 15Hawley et al. · 2014RCTA randomized placebo-controlled trial of manuka honey for radiation-induced oral mucositis [randomised controlled trial]View study →}. Systematic reviews of honey in this setting remain inconclusive and do not support it as standard care.

Gap: the two strongest trials are null; this is honey, not the herb, and tolerability during radiotherapy is a practical problem.

6. Antiviral

One methodologically clean in vitro study anchors this. A β-triketone-rich manuka oil showed virucidal activity against herpes simplex HSV-1 and HSV-2 in cell culture, reducing plaque formation by up to ~99% when virus was pre-treated before cell contact — i.e. it acts directly on free virus (likely the envelope) rather than inside infected cells ^{18Reference 18Reichling et al. · 2005In vitroVirucidal activity of a β-triketone-rich essential oil of Leptospermum scoparium (manuka oil) against HSV-1 and HSV-2 in cell culture [in vitro]View study →}. Reviews cite this as the principal antiviral evidence for the oil ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

Gap: a single in vitro study on one virus family, no replication and no human data; the effect requires direct oil-virus contact, so relevance beyond topical use is unclear.

7. Gingivitis

Small human trials of manuka honey for oral hygiene show modest benefit. A pilot RCT found chewing/applying a manuka honey product reduced plaque and gingival bleeding scores versus control ^{16Reference 16English et al. · 2004RCTThe effects of manuka honey on plaque and gingivitis: a pilot study [randomised controlled trial]View study →}, and a randomised field trial reported manuka-honey mouthwash improved plaque and gingival indices comparably to other honeys, though generally below chlorhexidine. A systematic review of honey in periodontal disease found positive but low-certainty antimicrobial and clinical signals ^{17Reference 17Hbibi et al. · 2020Systematic reviewAntimicrobial activity of honey in periodontal disease: a systematic review [systematic review]View study →}.

Gap: small, heterogeneous honey trials; the herb/oil is not what was tested, and effects trail standard chlorhexidine.

8. Anti-inflammatory

The weakest of the scored indications. Anti-inflammatory activity is asserted in reviews of the oil and inferred from its constituents ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}, and honey-based models show anti-inflammatory effects — but those test honey, not the leaf oil. The nearest human signal is a small clinical study in which topical manuka honey reduced atopic dermatitis lesion severity, attributed partly to immunoregulatory and anti-staphylococcal activity ^{13Reference 13Alangari et al. · 2017Clinical trialHoney is potentially effective in the treatment of atopic dermatitis: clinical and mechanistic studies [clinical trial]View study →}; again, this is the honey, not the herb, and it is not a dedicated trial of manuka as an anti-inflammatory.

Gap: constituent-level and honey-model inference only; no direct evidence for the herb as an anti-inflammatory.

Mechanisms

Clinical trials

Human trials exist only for manuka honey (topical wound care, oral mucositis, gingivitis) — the leaf and essential oil have no completed human trials and their evidence base is entirely preclinical.

Last checked: July 2026.

Dosage

There is no established internal dose for the manuka leaf or essential oil — the oil is a concentrated, chemotype-variable product used topically or aromatically (diluted), and its antibacterial/antifungal/antiviral evidence is entirely in vitro ^{1,4,18Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 4Christoph et al. · 2000In vitroA comparative study of the in vitro antimicrobial activity of tea tree oils with special reference to the activity of β-triketones [in vitro]View study →Reference 18Reichling et al. · 2005In vitroVirucidal activity of a β-triketone-rich essential oil of Leptospermum scoparium (manuka oil) against HSV-1 and HSV-2 in cell culture [in vitro]View study →}. The human dosing that exists is for manuka honey applied topically, not the herb, so the doses below cannot be back-converted to a dried-herb equivalent.

The entries above are manuka honey (topical) or in-vitro oil work; no marker-standardised internal preparation of the leaf or oil has been studied, so a dried-herb equivalent cannot be estimated.

Traditional Dosage

Traditional use is of the whole leaf as an infusion, decoction or topical preparation, and (separately) of the honey. The Western liquid-extract figure carried on this page is not backed by a located primary source and should be treated as indicative only.

Safety & Pregnancy

Manuka leaf and honey are well tolerated with a long food and topical record; the essential oil is a concentrated, chemotype-variable product for diluted topical or aromatic use only.

Full safety & interactions detail

Manuka is generally well tolerated: the leaf and manuka honey have a long record of food and topical use, and no serious adverse effects are documented in the clinical literature ^{11Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →}. The essential oil should be treated like any potent essential oil — it is for topical or aromatic use, diluted, and not for undiluted internal consumption; its composition (and therefore its irritancy) varies enormously by chemotype ^{2,3Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}. As a Myrtaceae species related to tea tree, topical contact allergy is plausible in sensitive individuals, though manuka-specific allergy reports are sparse. Manuka honey used as a wound dressing was, in one radiotherapy trial, poorly tolerated by mouth ^{15Reference 15Hawley et al. · 2014RCTA randomized placebo-controlled trial of manuka honey for radiation-induced oral mucositis [randomised controlled trial]View study →}, and its high fermentable-sugar content is a consideration for people managing blood glucose. As with all honey, it should not be given to infants under one year (botulism risk). Formal drug-interaction and cytochrome-P450 studies have not been conducted, so interactions are not assessed rather than established as absent.

The page’s traditional caution — take away from food, as astringent tannins may impede mineral absorption — is reasonable, but the broader claim that long-term use is safe rests on food-and-honey experience, not on trials of the leaf or oil.

References