Manuka

What Is Manuka?

Manuka is an evergreen shrub or small tree of New Zealand and south-east Australia, valued for its aromatic leaves and for the honey bees make from its flowers. Its leaves, bark and seeds were used in Māori medicine for skin complaints, colds, fevers and stomach upsets ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

Manuka grows throughout New Zealand, from the coast to the low alpine zone, and is also planted commercially for oil and honey ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}. The leaves are steam-distilled for an essential oil, and bees make manuka honey from its nectar.

The oil’s antimicrobial activity is linked to a group of compounds called β-triketones, chiefly leptospermone, and their amount varies widely with where the plant grew ^{1,3Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}. Manuka honey owes its antibacterial strength to a different compound, methylglyoxal, which forms in the honey rather than in the plant ^{25Reference 25Mavric et al. · 2008Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New ZealandView study →}. Laboratory studies of the oil and clinical trials of the honey have explored wound care, infection and oral health, with mixed results in people ^{1,9,14Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 9Jull et al. · 2015Systematic reviewHoney as a topical treatment for wounds [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 →}.

Manuka is often confused with kānuka (Kunzea species), a related shrub; manuka has prickly leaves and hard, persistent, nut-like fruits ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}. Its common name “tea tree” is also shared with Australian tea tree (Melaleuca alternifolia), a different plant with a different oil ^{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 →}.

How Is Manuka Used?

• Leaf — boiled or taken as a tea for colds and fevers, or crushed and applied to itchy skin and scabs, in Māori practice ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.
• Bark — used in Māori medicine for skin diseases, as a sedative and as a mouthwash ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.
• Essential oil — steam-distilled from the leaf and used diluted on the skin. Commercial oils vary in composition with their source ^{1,2Reference 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 →}.
• Honey — made by bees from manuka nectar and graded by its UMF (Unique Manuka Factor) rating. It is used as a wound and burn dressing and has been studied for gum health ^{9,11,16Reference 9Jull et al. · 2015Systematic reviewHoney as a topical treatment for wounds [systematic review]View study →Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →Reference 16English et al. · 2004RCTThe effects of manuka honey on plaque and gingivitis: a pilot study [randomised controlled trial]View study →}.

Traditional Uses

Māori Medicine

Manuka is one of the plants of Māori medicine (rongoā). The leaves were boiled in water for colds, taken as a tea for fevers and pain, and crushed and applied to ease itching and scabs ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

The bark was used for skin diseases, as a sedative and as a mouthwash. The seeds were given for dysentery and diarrhoea ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

Manuka and the other New Zealand and Australian “tea trees” were also used as topical preparations for wounds, cuts, sores and skin diseases, and as inhalations for colds and fevers ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

Botany

Manuka is an evergreen shrub or small tree in the myrtle family (Myrtaceae). It grows to about 12 m tall, and low, prostrate populations also occur in the wild ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}. Its bark is grey or reddish and peels in papery flakes ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}.

The leaves are small, 5–20 mm long, and most end in a stiff, prickly point ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}.

The flowers grow singly and are usually 10–20 mm across. They have five white petals, sometimes flushed pink, and usually a red centre ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}. The fruit is a hard, woody capsule 5–8 mm wide that stays on the branch ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}.

Manuka is a very variable species. Two varieties are recognised in New Zealand, and var. incanum, whose young growth is covered in long silky grey hairs, is confined to the north of the North Island ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}.

The leaf oil varies with where the plant grows. Oils from the East Cape of the North Island are high in β-triketones, oils from Northland are higher in pinene, and manuka grown in Australia contains almost no triketones ^{1,3Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}.

Distribution

Manuka grows throughout New Zealand, from the coast to low alpine habitats. It also occurs in south-east Australia, particularly Tasmania, although there is evidence that manuka in the strict sense is endemic to New Zealand ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}.

It is widely planted in revegetation schemes and grown in commercial plantations for oil and honey ^{26Reference 26Dawson et al. · 2020Leptospermum scoparium — species description, distribution and similar species — floraView study →}.

When myrtle rust reached New Zealand in 2017, every native member of the myrtle family was given a threat listing as a precaution, and manuka’s was At Risk – Declining. The 2023 reassessment returned it to Not Threatened ^{27Reference 27New Zealand Plant Conservation Network · 2026Leptospermum scoparium var. scoparium — conservation status history (NZ Threat Classification System 2017 and 2023) and myrtle rust threat — species database. https://www.nzpcn.org.nz/flora/species/leptospermum-scoparium-var-scoparium/View study →}.

Growing Conditions

Cultivation snapshot for Manuka

SunFull sunWaterMediumSoilAcidic, fertile, well-drainedLifeperennialZoneUSDA 9-10

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Farm Wiki is our cultivation-focused sister site, also run by Justin Cooke.

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Indications

• Wounds and burns [honey dressing] ⚠Caution: Cochrane reviews found that honey dressings heal partial-thickness burns faster than conventional dressings, but the evidence for most other wounds is of low quality. These trials tested honey in general, not manuka specifically ^9,10.
• Itchy skin, scabs and skin diseases [leaf and bark; Māori use]
• Eczema [honey, topical]
• Colds and fevers [leaf tea or inhaled vapour; Māori use]
• Pain [leaf tea; Māori use]
• Diarrhoea and dysentery [seed; Māori use]
• Mouth rinse [bark; Māori use]
• Plaque and gingivitis [honey]
• Cold sores [essential oil, topical]
• Scabies and skin mites [essential oil]
• Radiation-induced mouth sores [honey] ⚠Caution: Two placebo-controlled trials in people having radiotherapy for head and neck cancer found no benefit, and many patients could not tolerate the honey ^14,15.
• As a sedative [bark; Māori use]

Pharmacology & Research

Manuka research covers two products. The leaf essential oil has been studied almost entirely in the laboratory, in cell cultures and a few animal and veterinary models, for antibacterial, antifungal, antiviral and antiparasitic activity ^{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 →}. Manuka honey is the product tested in people, in trials of wound care, radiation-induced mouth sores and gum health ^{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 oil’s composition varies with where the plant grew, and most of its antimicrobial activity is linked to its β-triketone content ^{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 →}.

About six human trials have been completed, all of them of the honey. The leaf and essential oil have no completed human trials.

1. Antibacterial

The antibacterial activity belongs to the essential oil. Across New Zealand oils, potency tracks the β-triketone fraction, chiefly leptospermone with isoleptospermone and flavesone. It is strongest against Gram-positive bacteria, including Staphylococcus aureus and MRSA, and weaker 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 →}.

In leaf and branch extracts, the related β-triketone grandiflorone is the main antibacterial compound ^{7Reference 7Xu et al. · 2024In vitroTLC-bioautography-guided isolation and assessment of antibacterial compounds from manuka (Leptospermum scoparium) [in vitro]View study →}. A group of closely related nortriketones from the foliage are slightly less potent against Gram-positive bacteria ^{5Reference 5Killeen et al. · 2016In vitroNortriketones: antimicrobial trimethylated acylphloroglucinols from mānuka (Leptospermum scoparium) [in vitro]View study →}.

Leptospermone isolated from manuka seed oil inhibited six foodborne bacteria, with minimum inhibitory concentrations of 23.6–69.7 µg/mL ^{6Reference 6Jeong et al. · 2018In vitroAntimicrobial activities of leptospermone isolated from Leptospermum scoparium [in vitro]View study →}. Manuka oil is also active against bacteria that commonly infect scabies lesions, including Staphylococcus aureus and Streptococcus pyogenes ^{20Reference 20Taylor et al. · 2022In vitroInvestigating the antibacterial properties of prospective scabicides [in vitro]View study →}.

In veterinary work on Gram-negative bacteria from dogs with ear infections, the oil alone needed concentrations of 1% or more to inhibit growth. Adding the permeabilising agent Tris-EDTA lowered this to 0.06–0.5% ^{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 →}.

Manuka honey’s antibacterial action comes from methylglyoxal, not from the plant’s oil ^{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 →}.

Gap: every result is in vitro or veterinary. There are no human clinical trials of the oil as an antibacterial, and inhibitory concentrations vary widely with the oil’s source.

2. Wound Healing

The human wound evidence is for honey dressings, not the leaf or oil. A Cochrane review of 26 trials (3,011 participants) found high-quality evidence that honey dressings heal partial-thickness burns faster than conventional dressings, by about 4.7 days. Honey also healed infected post-operative wounds faster than antiseptic washes and gauze. Evidence for other wound types was of low or very low quality ^{9Reference 9Jull et al. · 2015Systematic reviewHoney as a topical treatment for wounds [systematic review]View study →}.

A Cochrane review of antiseptics for burns found moderate-certainty evidence that burns treated with honey are probably more likely to heal over time than those treated with topical antibiotics ^{10Reference 10Norman et al. · 2017Systematic reviewAntiseptics for burns [systematic review]View study →}.

Both reviews covered honey in general rather than manuka honey specifically.

In a randomised trial of 55 people having eyelid surgery, adding manuka honey to one side made no difference on validated scar scales. Patients did report less scar pain on the honey-treated side at four months ^{12Reference 12Malhotra et al. · 2017RCTEffect of manuka honey on eyelid wound healing: a randomized controlled trial [randomised controlled trial]View study →}.

The honey combines high sugar and osmolarity, 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 honey dressings, not the herb; certainty is low for most wound types, and the trials are varied.

3. Antifungal

The oil shows reproducible antifungal activity in vitro. In a comparison of Myrtaceae “tea tree” oils, manuka oil gave the best inhibition of dermatophytes, an effect attributed to its β-triketones ^{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 →}.

Reviews collate activity against Candida and Malassezia yeasts ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

Activity varies with the oil’s source. In one comparison, a South Island oil was more active against the moulds Aspergillus ochraceus and Fusarium culmorum than a North Island oil ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

All of this is in vitro work, and there are no human antifungal trials.

4. Antiparasitic

The β-triketones inhibit HPPD, an enzyme in tyrosine breakdown, and this is the proposed basis for their action on scabies mites. In vitro, manuka oil killed Sarcoptes scabiei mites and eggs more effectively than ivermectin, permethrin, tea tree or kunzea oil. Its activity tracked the three β-triketones, with leptospermone the strongest against eggs ^{19Reference 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 →}.

Against house-dust and stored-food mites, leptospermone was far more toxic than the benchmark agents benzyl benzoate and DEET ^{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 →}.

Manuka oil killed all cattle-tick (Rhipicephalus microplus) larvae at every concentration tested. Its triketone-rich fractions killed larvae, while its sesquiterpene-rich fraction was the most effective against engorged adult females ^{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 →}.

Leptospermone also caused rapid knockdown of Aedes aegypti mosquitoes. In mosquitoes it acts by inhibiting carbonic anhydrase rather than HPPD, and it was not toxic to ticks, honey bees or fruit flies ^{23Reference 23McComic et al. · 2025AnimalMode of toxicity of the β-triketone leptospermone to Aedes aegypti mosquitoes [animal model]View study →}.

Gap: all of this is in vitro, ex vivo or in arthropods. There are no clinical scabies or ectoparasite trials in people.

5. Oral Mucositis

Manuka honey has been tested for radiation-induced mouth sores (oral mucositis) in people with head and neck cancer, and both placebo-controlled trials were negative.

In 131 patients, 20 mL of active manuka honey four times daily for six weeks did no better than a golden-syrup placebo ^{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 →}.

In a second trial, 106 patients were randomised to swish and swallow 5 mL of manuka honey or a placebo gel four times daily. There was no significant difference in any outcome, and dropout was high in both arms (57% on honey, 52% on placebo), mostly because of nausea ^{15Reference 15Hawley et al. · 2014RCTA randomized placebo-controlled trial of manuka honey for radiation-induced oral mucositis [randomised controlled trial]View study →}.

Gap: both trials are null, this is honey rather than the herb, and tolerability during radiotherapy is a practical problem.

6. Antiviral

A β-triketone-rich manuka oil was virucidal against herpes simplex viruses in cell culture. When the virus was treated with the oil for an hour before infecting cells, plaque formation fell by 99.5% for HSV-1 and 98.9% for HSV-2 ^{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 →}.

Treating the cells beforehand had no effect, and once the virus was inside the cells the oil inhibited HSV-1 replication by only about 41%. Flavesone and leptospermone alone behaved like the whole oil ^{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 →}.

A later study reported that the oil also reduced the infectivity of acyclovir-resistant HSV isolates by more than 99% ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

The effect needs direct contact between oil and virus, which limits its relevance to topical use.

7. Gingivitis

Small human trials of manuka honey for oral hygiene show benefit. In a pilot trial, 30 volunteers chewed a manuka honey “leather” (UMF 15) or sugar-free gum for 10 minutes three times a day for 21 days. In the honey group mean plaque scores fell from 0.99 to 0.65, and bleeding sites from 48% to 17%, with no significant change in the gum group ^{16Reference 16English et al. · 2004RCTThe effects of manuka honey on plaque and gingivitis: a pilot study [randomised controlled trial]View study →}.

A systematic review of honey in periodontal disease included five randomised trials and eleven laboratory studies. Honey, most often manuka or multifloral, was active against all the gum-disease bacteria tested, but four of the five trials were at high risk of bias ^{17Reference 17Hbibi et al. · 2020Systematic reviewAntimicrobial activity of honey in periodontal disease: a systematic review [systematic review]View study →}.

Gap: the trials are small and varied, and the leaf and oil have not been tested.

8. Anti-Inflammatory

In cell work, manuka oil reduced the release of TNF-α from immune cells stimulated with bacterial endotoxin ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

The nearest human signal comes from the honey. In 14 adults with atopic dermatitis, manuka honey applied overnight for a week improved lesions compared with untreated lesions on the other side of the body. In the same study, the honey reduced an inflammatory chemokine in skin cells and inhibited mast-cell degranulation ^{13Reference 13Alangari et al. · 2017Clinical trialHoney is potentially effective in the treatment of atopic dermatitis: clinical and mechanistic studies [clinical trial]View study →}.

Gap: there are no controlled trials of the leaf or oil as an anti-inflammatory, and the atopic dermatitis study was small and uncontrolled.

Mechanisms

The oil’s β-triketones, chiefly leptospermone, are the plant’s own antimicrobial chemistry. They inhibit HPPD, the enzyme targeted by several commercial herbicides, and this has been studied as the basis of their action on scabies mites ^{5,19Reference 5Killeen et al. · 2016In vitroNortriketones: antimicrobial trimethylated acylphloroglucinols from mānuka (Leptospermum scoparium) [in vitro]View study →Reference 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 →}. In mosquitoes, leptospermone acts on carbonic anhydrase instead ^{23Reference 23McComic et al. · 2025AnimalMode of toxicity of the β-triketone leptospermone to Aedes aegypti mosquitoes [animal model]View study →}.

Manuka honey’s activity comes from its high sugar content and osmolarity, its low pH and methylglyoxal, which forms from nectar dihydroxyacetone as the honey matures ^{11Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →}.

Clinical Trials

Human trials exist only for manuka honey (topical wound care, radiation-induced mouth sores, gum health). The leaf and essential oil have no completed human trials.

Last checked: July 2026.

Phytochemistry

Commercial New Zealand manuka oil is dominated by sesquiterpene hydrocarbons, at 60% or more of the oil, with monoterpenes at 3% or less ^{2Reference 2Porter et al. · 1999In vitroChemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]View study →}. Its reported major components include leptospermone (0.8–19.4%), calamenene (2.5–18.5%) and flavesone (0.7–5.8%) ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}. One oil analysed for scabies work contained 17.2% leptospermone, 5.1% isoleptospermone, 4.7% flavesone and 42% sesquiterpenes ^{19Reference 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 →}.

The β-triketones carry most of the oil’s antimicrobial activity ^{2,4Reference 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 →}. In leaf and branch extracts, the related β-triketone grandiflorone is the main antibacterial compound, and a group of trimethylated relatives, the nortriketones, also occur in the foliage ^{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 →}.

Composition varies with region. Oils from 36 plants on the East Cape all contained more than 20% total triketones, and this high-triketone chemotype is localised there, with oils of up to 20% also found in the Marlborough Sounds ^{3Reference 3Douglas et al. · 2004In vitroEssential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]View study →}. Northland populations are higher in α- and β-pinene, and manuka grown in Australia contains almost no triketones ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}.

Manuka honey is a separate product. Its non-peroxide antibacterial activity comes from methylglyoxal, found in New Zealand manuka honeys at 38–761 mg/kg, up to 100 times the level in ordinary honey ^{25Reference 25Mavric et al. · 2008Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New ZealandView study →}. Methylglyoxal forms from nectar dihydroxyacetone as the honey matures and is not a constituent of the plant tissue ^{11Reference 11Nolan et al. · 2020Systematic reviewClinical significance of manuka and medical-grade honey for antibiotic-resistant infections: a systematic review [systematic review]View study →}.

Constituent Summary

Share of the steam-distilled leaf oil; values vary widely with region and chemotype.

Dosage

The essential oil is used diluted, on the skin or by inhalation. The human doses below are for manuka honey, not the leaf or oil.

Traditional Dosage

Safety & Pregnancy

Manuka leaf and honey have a long history of use. The essential oil is concentrated and varies in composition, so it is used diluted, on the skin or by inhalation.

Full Safety Detail

Essential oil. The oil is for diluted use on the skin or by inhalation, not for undiluted internal use. In safety testing of commercial preparations, a registered manuka oil had an oral LD50 of about 1,061 mg/kg in rats, and patch tests in 50 healthy volunteers at concentrations from 0.5% to 100% caused no significant irritation ^{1Reference 1Mathew et al. · 2020ReviewMānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]View study →}. Its composition, and so its irritancy, varies with where the plant grew ^{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 →}.

Skin sensitivity. Manuka belongs to the same family as tea tree, so contact allergy is possible in sensitive people, although manuka-specific reports are few.

Honey. Manuka honey used in the mouth during radiotherapy was poorly tolerated, mostly because of nausea ^{15Reference 15Hawley et al. · 2014RCTA randomized placebo-controlled trial of manuka honey for radiation-induced oral mucositis [randomised controlled trial]View study →}. Its sugar content is a consideration for people managing blood glucose. As with all honey, it should not be given to infants under one year because of the risk of botulism.

Interactions. No formal drug-interaction or cytochrome P450 studies have been carried out.

With food. Traditional advice is to take the leaf away from meals, because its astringent tannins may reduce mineral absorption.

References

1. Mathew, C., Tesfaye, W., Rasmussen, P., et al. (2020). Mānuka Oil — A Review of Antimicrobial and Other Medicinal Properties [review]. Pharmaceuticals (Basel). https://pubmed.ncbi.nlm.nih.gov/33114724/
2. Porter, N. G., & Wilkins, A. L. (1999). Chemical, physical and antimicrobial properties of essential oils of Leptospermum scoparium and Kunzea ericoides [in vitro]. Phytochemistry. https://pubmed.ncbi.nlm.nih.gov/9933953/
3. Douglas, M. H., van Klink, J. W., Smallfield, B. M., et al. (2004). Essential oils from New Zealand manuka: triketone and other chemotypes of Leptospermum scoparium [in vitro]. Phytochemistry. https://pubmed.ncbi.nlm.nih.gov/15184010/
4. Christoph, F., Kaulfers, P. M., & Stahl-Biskup, E. (2000). A comparative study of the in vitro antimicrobial activity of tea tree oils with special reference to the activity of β-triketones [in vitro]. Planta Medica. https://pubmed.ncbi.nlm.nih.gov/10985085/
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