Scientific Name(s): Leptospermum scoparium J.R. Forst. et G. Forst.
Common Name(s): Manuka honey, Manuka oil, Red manuka
Medically reviewed by Drugs.com. Last updated on Nov 20, 2023.
Manuka has selective antibacterial activity against Gram-positive organisms particularly S. aureus. Limited studies in wound healing and anti-inflammatory effects have been conducted.
Clinical trials are lacking on which to base dosing guidance.
Avoid use during pregnancy because of reported spasmolytic activity.
Documented adverse effects. Avoid use during pregnancy because of reported spasmolytic activity.
None well documented.
L. scoparium contains a lipophilic flavonoid that specifically interacts with benzodiazepine receptors (GABA-A receptor-chloride channel complex).
There are limited clinical toxicological data on both Manuka oil and Manuka honey.
- Myrtaceae (Myrtle)
L. scoparium is the only Leptospermum species native to New Zealand. Its size ranges from a creeping plant to a small tree (of 8 m in height) and it is widely distributed in various climatic and altitudinal zones in New Zealand. The physical characteristics, such as flower and leaf color, leaf size and shape, branching habit, and foliage density vary considerably among populations. Manuka oil should not be confused with Melaleuca alternifolia (see Tea Tree Oil monograph).Melching 1997, Porter 2001, Porter 1999, USDA 2017
Early New Zealand records indicate that the plant's bark, leaves, sap, and seed capsules were used in beverages and medicinal preparations.Porter 1999 The plant was valued for its medicinal properties and wood by the indigenous Maori people; the wood was utilized for gardening tools, fishing, housing structures, and weapons.Porter 2001, Riley 1994
Captain James Cook used the leaves of the plant as a tea to combat scurvy during long explorations of the southern hemisphere; early European settlers of New Zealand adopted Captain Cook's use of the plant as a tea.Porter 2001
Commercial development of the essential oils has led to a range of OTC products marketed in New Zealand and exported to European and Asian markets. These products are used for topical treatment of various conditions including the following: Fungal and bacterial skin infections; inflammation from sunburn, insect bites, or joint pain; eczema or psoriasis. The oils also are used in perfumes and soaps.Porter 2001
Manuka essential oil is extracted from the leaves of the plant, while Manuka honey is produced by bees. The L. scoparium populations of New Zealand are highly variable in oil chemical composition and activity.(Perry 1997, Priest 2002) Standardized steam distillation and gas chromatography-mass spectrometry of the essential oils of 15 New Zealand L. scoparium populations identified the following in various quantities per species: alpha-pinene, beta-pinene, myrcene, rho-cymene, 1,8-cineole, linalol, methylcinnamate, alpha-farnesine, isoleptospermone, leptospermone, sesquiterpenes such as cadina-3,5-diene and delta-amorphene, and triketones.(Melching 1997, Porter 1999, Perry 1997)
Triterpenoids and flavonoids (including methylated and methoxylated flavonoids such as 5,7-dimethoxyflavone, 5-hydroxy-7-methoxy-6-methylflavone, and 5-hydroxy-7-methoxy-6,8-dimethylflavan-3-one) have been identified in a dichloromethane extract of L. scoparium.(Häberlein 1994, Häberlein 1998) Oligosaccharide components include maltose (the major component), isomaltose (or maltulose), kojibiose, turanose (or gentiobiose), and nigerose.(Weston 1999)
The average content of total flavonoids in New Zealand manuka (L. scoparium) honey was 3.06 mg per 100 g honey; the main flavonoids consisted of quercetin, isorhamnetin, chrysin, and luteolin.(Yao 2003) The potentially active methylglyoxal, derived from the precursor dihydroxyacetone, has been identified in the flowers of certain species of Leptospermum native to New Zealand and Australia, and is found in Manuka honey.(Carter 2016, White 2016) Interestingly, soil fertility may be a determiner of Manuka honey quality.(Meister 2021)
Uses and Pharmacology
Animal and in vitro data
Manuka oil has selective antibacterial activity against gram positive organisms(Harkenthal 1999) such as Staphylococcus aureus and Micrococcus luteus.(Rhee 1997) Manuka oil has little to no activity against gram-negative organisms such as Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Proteus vulgaris.(Harkenthal 1999, Kim 1999, Rhee 1997)
In vitro, Manuka honey effectively inhibited biofilm formation by C. difficile strains of different polymerase chain reaction ribotypes.(Piotrowski 2017)
In vitro experiments concluded that Manuka oil may be an effective alternative to antibiotics for the treatment of topical staphylococcal infections.(Fratini 2017) A review found extensive in vitro data supporting the antimicrobial effects of Manuka oil and suggested further clinical studies to establish its therapeutic potential. Clinical evidence on Manuka oil's efficacy, safety, and dosing guidelines are necessary for its implementation for medical purposes.(Mathew 2020)
Studies have evaluated the efficacy of Manuka honey in healing infected wounds. In neuropathic diabetic foot ulcers, Manuka honey-impregnated dressings increased healing rates and reduced the need for antibiotics in a clinical study of 63 patients versus saline dressings. However, the percentage of healed ulcers was not affected.(Kamaratos 2014) While the role of honey as an anti-infective agent has been described, the additive efficacy of Manuka in the honey has not been established in robust clinical trials.(Carter 2016, White 2016)
Anti-inflammatory and immunomodulatory effects have been described in published reviews.(White 2016)
A small clinical trial (n=19) evaluated Manuka with Kanuka essential oils as a gargle for benefit on radiotherapy-induced mucositis and symptoms. Mucositis reportedly developed significantly later in patients with the active gargle. The small sample size of most of the variables prevented further statistical comparisons. Mean pain scores gradually increased over treatment time with fewer patients in the active gargle group experiencing scores of 3 or higher and going the longest until that level of pain was reached; this was also reflected in the use of daily analgesics. Interestingly, patients with more family members present during treatment tended to report more frequent and more severe pain than those without family members present.(Maddocks-Jennings 2009)
Manuka, as the honey, has been studied in radiotherapy-induced mucositis in limited clinical trials finding no improvement on mucositis, and some effect on bacterial infection.(Bardy 2012, Hawley 2014)( Bardy, Hawley) A study conducted in patients with rhinosinusitis, using mankua honey nasal spray, found no endoscopically validated improvement in symptoms.(Thamboo 2011)
The in vitro activity of Manuka oil was analysed by agar disk diffusion and minimum inhibitory concentration methods. The results demonstrated the efficacy of Manuka essential oils and supported their application as a natural alternative treatment against Candida spp.(Elisa 2021)
L. scoparium essential oil is a promising source of mosquito larvicide and its toxicity is enhanced by a biobased emulsifier.(Muturi 2020)
The pharmacological action of Manuka oil for treating diarrhea, colds, and inflammation was studied on a field-stimulated guinea pig ileum. Manuka oil induced a spasmolytic effect(Lis-Balchin 2000, Lis-Balchin 1998); the mechanism of action is likely to be the result of a postsynaptic mechanism and associated with cAMP.(Lis-Balchin 1998)
L. scoparium contains a lipophilic flavonoid that specifically interacts with benzodiazepine receptors in the GABA-A receptor-chloride channel complex. A sedating and potentially anxiolytic effect was recorded in a locomotion study with rats.(Häberlein 1994, Häberlein 1994)
There is currently not enough evidence to recommend the use of Manuka honey for atopic dermatitis therapy.(Shi 2019)
There are no reported clinical studies of Manuka oil on which dosage recommendations can be based.
Manuka honey has been used anecdotally as a probiotic. A study evaluated the safety of consuming 20 g of honey daily for 4 weeks and found no adverse effects on GI flora.(Wallace 2010) 20 mL of the honey taken 4 times daily for 6 weeks was evaluated in oral mucositis.(Bardy 2012)
Pregnancy / Lactation
None well documented.
There are limited clinical toxicological data on Manuka oil in the scientific literature. Anecdotal information from OTC use of topical Manuka oil products suggest good potential for its future use as an antimicrobial agent.(Porter 2001) Avoid use during pregnancy because of reported spasmolytic activity.(Lis-Balchin 2000, Lis-Balchin 1998)
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