Lemon myrtle (Backhousia citriodora), a rainforest tree native to subtropical Australia, packs a remarkably potent chemistry into its fragrant leaves. Its essential oil contains the highest natural concentration of citral found in any plant, and lab research links this compound and the leaf’s polyphenols to genuine antimicrobial, antioxidant, anti-inflammatory, and even dental-health benefits. While most of the evidence comes from cell and lab studies rather than large human trials, the findings are consistent, well-replicated, and increasingly hard to dismiss as mere folklore.
The Chemistry Behind the Benefits
If you crush a lemon myrtle leaf between your fingers, the intense citrus burst you smell is almost entirely citral, a mixture of two closely related molecules called geranial and neral. Gas chromatography analysis of the essential oil found that geranial made up about 52% and neral about 38% of the total oil content, meaning citral accounts for roughly 90% of the oil overall.1PubMed Central. Chemical Composition, Antioxidant, Antibacterial, and Antibiofilm Activities of Backhousia citriodora Essential Oil That concentration dwarfs what you find in lemongrass or lemon verbena, both of which are better known but contain far less citral per unit of oil.
Citral matters because it is the compound responsible for most of lemon myrtle’s antimicrobial punch. But the leaves also contain a diverse set of polyphenols, including ellagic acid, quercetin, hesperetin, and myricetin, which contribute antioxidant and anti-inflammatory effects that citral alone does not fully explain.2Bioscience, Biotechnology, and Biochemistry. Lemon myrtle extract inhibits lactate production by Streptococcus mutans So the health story of lemon myrtle is really two stories layered on top of each other: a volatile oil that kills microbes, and a polyphenol-rich leaf extract that calms inflammation and scavenges free radicals.
Broad-Spectrum Antimicrobial Activity
The antimicrobial evidence for lemon myrtle is unusually broad. The essential oil has shown significant activity against both gram-positive bacteria like Staphylococcus aureus (including methicillin-resistant strains, or MRSA) and gram-negative bacteria like E. coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, as well as the yeast Candida albicans, the mold Aspergillus niger, and the acne-associated bacterium Propionibacterium acnes.3Food and Chemical Toxicology. Toxicity of Australian essential oil Backhousia citriodora (Lemon myrtle). Part 1. Antimicrobial activity and in vitro cytotoxicity That range covers a lot of real-world trouble, from food-borne illness to hospital-acquired infections to common skin complaints.
Further testing using microdilution methods confirmed that the oil is especially potent against gram-positive species. Staphylococcus epidermidis, a skin bacterium involved in implant infections, was the most sensitive, producing an inhibition zone of roughly 50 mm in disk diffusion assays. S. aureus was next, followed by E. coli and K. pneumoniae.1PubMed Central. Chemical Composition, Antioxidant, Antibacterial, and Antibiofilm Activities of Backhousia citriodora Essential Oil The oil also proved to be a strong antibiofilm agent, inhibiting new biofilm formation by 85% to 96% and breaking down established biofilms by 71% to 91% across four bacterial strains, performance that compared favorably to streptomycin, a conventional antibiotic.1PubMed Central. Chemical Composition, Antioxidant, Antibacterial, and Antibiofilm Activities of Backhousia citriodora Essential Oil
Biofilms are the slimy, protective colonies that bacteria build on surfaces, from kitchen counters to medical devices to your own teeth. They are notoriously difficult to penetrate with standard disinfectants, which is why lemon myrtle’s dual ability to both prevent new biofilms and break apart existing ones is worth paying attention to.
Antifungal Effects and Candida
The antimicrobial story extends to fungi in a meaningful way. A 2025 study specifically examined lemon myrtle extract against Candida species, the yeasts responsible for oral thrush, vaginal yeast infections, and dangerous bloodstream infections in immunocompromised patients. The extract significantly reduced Candida’s ability to adhere to hard surfaces and inhibited biofilm formation. It also suppressed several of the yeast’s virulence tools, including phospholipase production, protease activity, and the shift to a hyphal form that lets Candida invade tissues.4PubMed. Suppressive effects of lemon myrtle extract against the colonization and virulence factors of Candida spp.
This matters because antifungal drug resistance is a growing problem. If a plant extract can strip Candida of its key invasion machinery rather than just trying to kill it outright, it could work alongside conventional antifungals or help prevent infections from gaining a foothold in the first place. The research is still at the lab bench, not the clinic, but the mechanism is promising.
A Tested Treatment for a Common Childhood Skin Condition
One of the few controlled human trials involving lemon myrtle targeted molluscum contagiosum, a viral skin infection that produces clusters of small, pearly bumps and is extremely common in young children. Thirty-one children (average age around four and a half years) were randomized to receive either a 10% lemon myrtle oil solution applied once daily or a plain olive oil vehicle. After 21 days, more than half of the children treated with lemon myrtle oil saw a greater than 90% reduction in the number of lesions, while none of the children in the olive oil group met that benchmark. No adverse events were reported.5PubMed. Essential oil of Australian lemon myrtle (Backhousia citriodora) in the treatment of molluscum contagiosum in children
Molluscum contagiosum is usually self-limiting, meaning it eventually goes away on its own, but “eventually” can mean months or even years, and the bumps spread easily between children. Standard treatments like cryotherapy (freezing) are painful and often poorly tolerated by small kids. A painless topical oil that clears lesions in three weeks is a genuinely useful result, even from a small trial. It remains one of the strongest pieces of clinical evidence for any lemon myrtle application.
Oral Health and Cavity Prevention
Some of the most interesting recent research focuses on the mouth. Streptococcus mutans is the primary bacterium behind dental cavities: it glues itself to teeth using sticky glucans, builds biofilms (dental plaque), and then produces lactic acid that eats into enamel. Lemon myrtle extract targets multiple stages of this process. It strongly inhibited the glucosyltransferase enzymes S. mutans uses to manufacture its sticky biofilm scaffold, achieving the highest inhibitory activity among all plant extracts tested in one study.6Bioscience, Biotechnology, and Biochemistry. A lemon myrtle extract inhibits glucosyltransferases activity of Streptococcus mutans
A follow-up study dug into the acid side of the problem. S. mutans produces lactic acid through glycolysis, and that acid is what actually dissolves tooth enamel. Lemon myrtle extract reduced lactate production by at least 46% and slowed the glycolytic pH drop in bacterial culture. Researchers traced the effect to the polyphenols in the extract: ellagic acid, quercetin, hesperetin, and myricetin all independently reduced the pH drop, lactate output, and viable bacterial counts.2Bioscience, Biotechnology, and Biochemistry. Lemon myrtle extract inhibits lactate production by Streptococcus mutans
Taken together, the evidence suggests that lemon myrtle could serve as a functional ingredient in mouthwashes or toothpastes: reducing plaque formation while also dampening the acid attack that causes cavities. No commercial product trials have been published yet, but the mechanistic picture is coherent enough that dental researchers are paying attention.
Antioxidant and Anti-Inflammatory Properties
Beyond killing microbes, lemon myrtle leaf extracts demonstrate clear antioxidant capacity in standard lab assays, effectively scavenging the two most commonly used test radicals.7PubMed Central. Anti-inflammatory and anti-oxidative activities of lemon myrtle (Backhousia citriodora) leaf extract Antioxidant test-tube results are sometimes dismissed as irrelevant to what happens in the human body, and that skepticism is fair. But the anti-inflammatory findings are harder to wave away, because they involve a meaningful biological mechanism.
When immune cells called macrophages are stimulated with bacterial toxins in a dish, they release a cascade of inflammatory mediators. Lemon myrtle leaf extract inhibited the production of nitric oxide, a key inflammatory signaling molecule, in stimulated macrophage cultures.7PubMed Central. Anti-inflammatory and anti-oxidative activities of lemon myrtle (Backhousia citriodora) leaf extract A separate study confirmed the anti-inflammatory effect using phenolic compounds specifically extracted from the leaves, again showing inhibition of nitric oxide in the same cell model.8PubMed Central. Antioxidant and anti-inflammatory activities of phenolic compounds extracted from lemon myrtle (Backhousia citriodora) leaves at various extraction conditions
Nitric oxide suppression matters because chronic overproduction of this molecule is linked to joint inflammation, gut inflammation, and many other persistent inflammatory conditions. If lemon myrtle polyphenols survive digestion and reach tissues at relevant concentrations, they could genuinely help. That “if” is the main gap in the evidence: no human study has measured whether drinking lemon myrtle tea or taking a supplement actually lowers inflammatory markers in the blood. The cell-culture work is encouraging, but it is a starting point, not a finish line.
Potential Metabolic Benefits
One intriguing finding sits at the intersection of lemon myrtle and blood sugar management. Polyphenol-rich fractions from lemon myrtle leaves were tested in the lab for their ability to inhibit alpha-glucosidase, the enzyme in your gut lining that breaks complex carbohydrates into absorbable sugars. Lemon myrtle showed pronounced inhibitory activity, and in fact performed as the most potent alpha-glucosidase inhibitor among the three native Australian herbs tested, outperforming both anise myrtle and Tasmannia pepper leaf.9PubMed. Composition of native Australian herbs polyphenolic-rich fractions and in vitro inhibitory activities against key enzymes relevant to metabolic syndrome
Alpha-glucosidase inhibition is the exact mechanism used by a well-known class of diabetes medications. By slowing carbohydrate digestion, these drugs blunt the post-meal blood sugar spike that is so damaging in type 2 diabetes. Whether lemon myrtle tea or a supplement could produce a similar effect in a living human is unknown. The concentrations used in lab assays often exceed what you could reasonably achieve through dietary intake. Still, the finding is worth noting because it points lemon myrtle’s polyphenols toward a specific, well-understood biological pathway rather than vague “superfood” hand-waving.
The same study tested for inhibition of pancreatic lipase (a fat-digesting enzyme) and found lemon myrtle was less effective there, so the metabolic interest centers on sugar metabolism rather than fat absorption.9PubMed. Composition of native Australian herbs polyphenolic-rich fractions and in vitro inhibitory activities against key enzymes relevant to metabolic syndrome
Food Preservation
Outside of personal health, lemon myrtle oil has attracted interest as a natural food preservative. Its broad-spectrum antimicrobial activity extends to fungi that cause post-harvest spoilage of fruit and other fresh produce.10ScienceDirect. Essential Oils in Food Preservation, Flavor and Safety As consumers increasingly resist synthetic preservatives, food scientists have been screening botanical essential oils for ones that can extend shelf life without altering taste. Lemon myrtle is a strong candidate because the same citral that kills microbes also imparts a pleasant citrus flavor, so it doubles as a flavoring agent. Australian food manufacturers already use lemon myrtle in baked goods, sauces, teas, and condiments, where its preservative role is a useful bonus on top of its culinary appeal.
Safety and Concentration Matters
Lemon myrtle tea, made from dried leaves, is widely consumed in Australia and is generally considered safe. The essential oil, however, is a different story at higher concentrations. A toxicology study applied lemon myrtle oil directly to excised human skin samples and found that at meaningful exposure levels, the oil caused significant damage to the outer skin barrier, including degradation of the stratum corneum, cellular death in up to 15% of cells, and abnormal fluid-filled pockets (vacuolation) in up to 25% of cells.11PubMed. Toxicity of Australian essential oil Backhousia citriodora (lemon myrtle). Part 2. Absorption and histopathology following application to human skin
When the oil was formulated into a product containing just 1% lemon myrtle oil and applied under the same conditions, actual absorption of citral through the skin was extremely low and the histological damage was limited.11PubMed. Toxicity of Australian essential oil Backhousia citriodora (lemon myrtle). Part 2. Absorption and histopathology following application to human skin This lines up with the molluscum contagiosum trial, which used a 10% dilution and reported no adverse events over three weeks of daily use.5PubMed. Essential oil of Australian lemon myrtle (Backhousia citriodora) in the treatment of molluscum contagiosum in children The practical takeaway: never apply undiluted lemon myrtle essential oil to your skin. Diluted properly in a carrier oil or formulated into a product at concentrations up to about 10%, it appears well tolerated. Above that, citral’s irritant properties dominate.
Citral is also a known contact sensitizer, meaning some people can develop an allergic skin reaction to it with repeated exposure. If you are going to use lemon myrtle oil topically, a patch test on a small area of skin first is sensible, especially if you have a history of fragrance sensitivity.
How People Actually Use It
In practice, lemon myrtle shows up in daily life in several forms. The dried leaf is the mildest and most common: steeped as a herbal tea, added to baking, blended into spice mixes, or sprinkled over seafood. Australian bushfood cuisine has used it this way for a long time, and it has been gaining popularity in specialty food markets worldwide. As a tea, it delivers polyphenols and some citral in a gentle, food-safe form.
The essential oil is used in aromatherapy diffusers for its bright citrus scent, in natural cleaning products for its antimicrobial properties, and in skincare formulations at low concentrations. You will find it in natural deodorants, insect repellents, and hand sanitizers marketed as plant-based alternatives to chemical formulations. Its effectiveness in these applications varies, but the antimicrobial data at least supports the idea that it is doing something beyond smelling nice.
Concentrated supplements in capsule form also exist, typically standardized to citral or total polyphenol content. These sit in a regulatory grey area in most countries, sold as dietary supplements without specific health claims. Given the absence of human dose-response studies, there is no established therapeutic dose for any condition, and anyone considering a supplement should recognize that the promising lab results do not automatically translate to a pill working the same way in the body.
Where the Evidence Stands Compared to the Hype
Lemon myrtle is sometimes marketed with the kind of breathless enthusiasm reserved for the latest superfood. The reality is more specific and more interesting than generic “boosts immunity” claims. The antimicrobial data is robust and consistent across multiple independent labs. The molluscum contagiosum trial is a genuine, if small, clinical win. The oral health findings target a precise mechanism with clear relevance to cavity prevention. The anti-inflammatory and metabolic data point in encouraging directions without yet proving anything in humans.
What is missing is the middle layer of evidence: well-designed human trials measuring bioavailability (whether the active compounds actually reach relevant tissues after you drink the tea or swallow the capsule), dose-response relationships, and long-term safety. For the essential oil used topically, the evidence base is further along because skin application bypasses the digestion question. For oral consumption, the gap between lab dish and living person remains wide. Researchers working with lemon myrtle seem well aware of this, and several groups have flagged clinical trials as the necessary next step. Until those trials materialize, the honest framing is that lemon myrtle is a plant with unusually strong and well-characterized bioactive chemistry, a handful of proven topical applications, and a lot of reasonable but unconfirmed potential for broader health benefits.