Lemongrass Antimicrobial Effects and Oral Health

This is lemongrass's strongest laboratory suit and its weakest clinical one, and the distance between those two facts is where almost every exaggerated claim about the plant comes from. In a petri dish, lemongrass essential oil is genuinely impressive: it inhibits a broad range of bacteria including Staphylococcus aureus and Escherichia coli, it disrupts biofilms, and it is one of the more reliably active essential oils against Candida yeasts. Those results have been reproduced by many independent groups. They are not controversial.

What they are, however, is in vitro. Almost the entire antimicrobial literature on this plant consists of the oil applied directly to organisms in a well, on a plate, or in a vapour chamber — at concentrations that are trivial to create in glassware and impossible to create safely inside a human body. The handful of human studies that exist are small, and all of them are topical: an oral rinse for thrush, a mouthwash, a scalp tonic. Not one is a study of swallowing lemongrass to fight an infection, and nobody should be trying that. This page separates the two carefully, gives the in-vitro work its due, and then says plainly what it does and does not license.

Table of Contents

1. Once More: This Is the Oil, Not the Tea
2. The In-Vitro Antibacterial Record
3. Reading an MIC Without Being Fooled
4. Candida and the Antifungal Data
5. Biofilms and Why They Matter
6. Oral Thrush: The One Human Infection Study
7. Mouthwash, Plaque and Gingivitis
8. Halitosis and the Deodorant Effect
9. Dandruff and the Species Confusion
10. Food Preservation and Household Use
11. Why This Is Not an Antibiotic
12. How to Use It Safely
13. Safety and Cautions
14. Key Research Papers
15. Connections

Once More: This Is the Oil, Not the Tea

Every antimicrobial number quoted on this page comes from lemongrass essential oil or from purified citral — not from a cup of lemongrass tea. The distinction is not pedantry:

• Composition. The oil is a steam distillate, typically 70–85% citral, with geraniol, citronellal, limonene, myrcene and geranyl acetate making up most of the remainder. A leaf infusion is mostly water-soluble flavonoids — luteolin and apigenin derivatives — plus tannins and a small carryover of citral.
• Concentration. In-vitro antimicrobial testing of essential oils routinely uses concentrations in the range of hundreds to thousands of micrograms per millilitre, and often percentages of oil by volume. Nothing remotely like that is present in a mug of tea.
• Route. The human studies are mouth rinses and scalp applications — the oil in contact with the target surface. There is no study of swallowed lemongrass oil for an infection, and there is no safe dose to build one on.

So the correct reading of "lemongrass kills MRSA in the lab" is: a concentrated distillate, applied directly to bacteria growing on a plate, at a concentration achieved in glassware, inhibited their growth. That is a legitimate and interesting result. It is not a reason to drink anything, and it is not a reason to skip an antibiotic.

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The In-Vitro Antibacterial Record

Evidence tier: preliminary (in vitro). The antibacterial literature on lemongrass oil is large and consistent. Representative work includes Antibacterial activity of lemongrass (Cymbopogon citratus) oil against some selected pathogenic bacteria by Naik, Fomda, Jaykumar and Bhat in the Asian Pacific Journal of Tropical Medicine in 2010, which screened the oil against a panel of clinical isolates, and Lemon grass (Cymbopogon citratus) essential oil as a potent anti-inflammatory and antifungal drug by Boukhatem, Ferhat, Kameli, Saidi and Kebir in the Libyan Journal of Medicine in 2014.

Across this literature, the pattern is:

• Gram-positive organisms are hit hardest — staphylococci and streptococci are typically the most susceptible, including methicillin-resistant S. aureus in some screens. Work such as Warnke and colleagues' survey of antimicrobial essential oils against hospital-acquired pathogens placed lemongrass among the more active oils tested.
• Gram-negative organisms are less susceptible but not immune — E. coli, Klebsiella, Salmonella, Pseudomonas and others are inhibited, generally at higher concentrations, because the outer membrane of a Gram-negative cell is a real barrier to lipophilic terpenes.
• The mechanism is membrane disruption. Citral and other monoterpenes partition into the lipid bilayer, increase permeability, cause leakage of ions and cell contents, and collapse the membrane potential. This is a physical, non-specific mechanism — which explains both the broad spectrum and the fact that it does not spare human cells at high concentrations.
• Vapour-phase activity is real. Several studies show inhibition when the oil is not in contact with the agar at all, only sharing headspace — relevant to food packaging and to fungal spoilage.

None of this has been translated into a systemic human antibacterial treatment, and the membrane mechanism is a large part of why: a compound that dissolves microbial membranes at a given concentration is not selective enough to circulate in blood at that concentration.

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Reading an MIC Without Being Fooled

The single most useful skill for reading this literature is knowing what a minimum inhibitory concentration (MIC) means and what it does not.

An MIC is the lowest concentration of a substance that prevents visible growth of an organism under specific laboratory conditions. It is a property of the substance and the assay — the medium, the inoculum size, whether an emulsifier was used, whether growth was read at 24 or 48 hours. Essential-oil MICs vary widely between papers for exactly these reasons, which is why you should be suspicious of any article quoting one number as if it were a physical constant.

Then ask the question that dissolves most exaggerated claims: could a human body ever reach this concentration at the site of infection?

• For a surface — skin, mouth, a countertop, the outside of a food — the answer is often yes. You can apply a 0.25% or 1% preparation directly, and the concentration at the target is whatever you made it. This is why the only positive human lemongrass studies are topical.
• For the bloodstream or a deep tissue, the answer is essentially always no. To reach an antibacterial concentration systemically you would have to swallow or inject an amount of concentrated citral that would injure you first. Essential oils are also rapidly metabolised and cleared.

Two further reality checks. In-vitro tests use clean, planktonic bacteria in nutrient broth — not organisms embedded in pus, biofilm, necrotic tissue or a protein-rich exudate, all of which bind and inactivate lipophilic compounds. And in-vitro tests have no immune system either helping or being harmed. The gap between a plate and a patient is not a technicality; it is where the great majority of promising antimicrobials die.

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Candida and the Antifungal Data

Evidence tier: preliminary (in vitro). The antifungal data are, if anything, more consistent than the antibacterial data. Antifungal activity of the lemongrass oil and citral against Candida spp. by Silva, Guterres, Weisheimer and Schapoval in the Brazilian Journal of Infectious Diseases in 2008 tested both the whole oil and isolated citral against multiple Candida species and found activity in both, indicating that citral carries much of the effect. Tyagi and Malik reported liquid- and vapour-phase antifungal activity of Cymbopogon citratus oil against Candida albicans in BMC Complementary and Alternative Medicine in 2010, with microscopy showing gross damage to the fungal cell envelope. Boukhatem's 2014 paper reached similar conclusions.

Fungal cells, like bacterial cells, have membranes that monoterpenes partition into; the mechanism is the same physical disruption, sometimes with additional effects on ergosterol-containing membranes and on the yeast-to-hyphal transition that Candida uses to invade tissue.

What this supports: interest in lemongrass oil for surface and mucosal antifungal applications, which is exactly where the one human study went.

What it does not support: treating any invasive or systemic fungal infection, treating vaginal candidiasis with undiluted oil (a route that causes chemical burns), or the ill-defined internet construct of "systemic candida overgrowth."

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Biofilms and Why They Matter

Evidence tier: preliminary (in vitro). A biofilm is a community of microbes embedded in a self-produced matrix, stuck to a surface. Dental plaque is a biofilm; so is the slime on a catheter, and much of chronic wound and sinus infection. Biofilm organisms can be tens to hundreds of times harder to kill than the same species floating free, which is why biofilm-active agents attract attention.

Lemongrass oil and citral have been reported to reduce biofilm formation and to disrupt established biofilms in several in-vitro models, including the dental caries organism Streptococcus mutans. The plausible reason is again mechanical rather than clever: a membrane-disrupting terpene does not care whether a cell is in a biofilm, and the oil's lipophilicity may help it penetrate the matrix where water-soluble antiseptics struggle.

This is genuinely the most interesting frontier for lemongrass, and it is also where the hype gets furthest ahead of the evidence. Anti-biofilm activity on a polystyrene plate is not clinical efficacy against dental plaque in a mouth, where saliva dilutes everything, the biofilm regrows within hours, and mechanical removal by a toothbrush remains the dominant intervention. PubMed topic search: Cymbopogon citratus, citral and biofilm inhibition.

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Oral Thrush: The One Human Infection Study

Evidence tier: preliminary human. The study is Treatment of oral thrush in HIV/AIDS patients with lemon juice and lemon grass (Cymbopogon citratus) and gentian violet, by Wright, Maree and Sibanyoni, published in Phytomedicine in 2009. It was conducted in a South African setting where access to conventional antifungals was limited, and it compared inexpensive, locally available topical treatments for oral candidiasis in people with HIV/AIDS.

The design compared lemon juice, lemongrass infusion and gentian violet as topical oral treatments, with clinical resolution of thrush as the endpoint, and reported benefit from the plant-based arms. Read in context, this is a pragmatic, resource-appropriate study asking a real question: when the standard drug is unavailable, does a cheap local option help?

Its limits are substantial and should be stated:

• Small, open-label, and conducted in a specific population and setting.
• The comparator was another topical agent, not a modern antifungal such as fluconazole or nystatin.
• It does not establish that lemongrass should be chosen where effective antifungals are available — it establishes that something is better than nothing.
• The intervention was applied in the mouth. It is a topical mucosal treatment, not a systemic one.

What it does contribute is important: it is the only human study in which lemongrass was used against an actual infection and something measurable happened. That places it above the in-vitro literature and well below a randomized trial against standard care.

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Mouthwash, Plaque and Gingivitis

Evidence tier: preliminary human (small clinical study). The dental literature contains a three-arm study of a 0.25% lemongrass oil mouthwash compared with chlorhexidine and a control, reported in the Journal of Clinical and Diagnostic Research in 2015, with plaque and gingival indices as endpoints. Small studies of this shape are a staple of the dental-materials literature and they are useful as a first pass, with familiar caveats: short duration, small samples, single centre, and outcome indices that are examiner-scored.

The relevant background is that chlorhexidine is the benchmark antiseptic mouthwash and a demanding comparator — it substantively reduces plaque and gingivitis, and its problems are tolerability rather than efficacy (tooth staining, taste disturbance, calculus). Any plant-oil rinse is being measured against a high bar, and essential-oil mouthwashes as a class do have real supporting evidence — the long-established thymol/eucalyptol/menthol/methyl-salicylate formulation is the best-studied example. Lemongrass is a plausible member of that class with a fraction of the data.

Honest bottom line for gingivitis and plaque: a lemongrass-oil rinse is a reasonable adjunct with preliminary support, and it is not a substitute for brushing, flossing or professional cleaning. Nothing in a bottle removes plaque as well as mechanical disruption does, and periodontitis requires professional treatment, not a rinse.

Also — and this matters — a mouthwash is swished and spat. Do not make a stronger one on the theory that more is better, and do not swallow it. A 0.25% preparation is a fortieth of the strength of neat oil, and that dilution is the point.

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Halitosis and the Deodorant Effect

Evidence tier: preliminary, largely mechanistic. Most persistent bad breath originates in the mouth, from anaerobic bacteria on the tongue and in periodontal pockets producing volatile sulphur compounds. Two things could in principle help: reducing the bacteria, and masking or chemically neutralising the odour.

Lemongrass oil is plausibly capable of both — it has in-vitro activity against oral anaerobes, and it is a strong, clean-smelling aromatic. But the second effect is cosmetic and short-lived, and the first has not been demonstrated clinically for halitosis. Masking is worth knowing about precisely because it is so easy to mistake for treatment: if a rinse makes your breath smell of lemon for twenty minutes, that is not evidence that the underlying cause changed.

The interventions with actual evidence for halitosis are tongue cleaning, treating gum disease, treating dental decay, and managing dry mouth. If bad breath persists despite good oral hygiene, it needs a dental assessment rather than a stronger mouthwash. See also Oil Pulling for a related practice with similarly thin evidence.

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Dandruff and the Species Confusion

Evidence tier: preliminary human (controlled). The study is Anti-dandruff hair tonic containing lemongrass (Cymbopogon flexuosus) oil, by Chaisripipat, Lourith and Kanlayavattanakul in Complementary Medicine Research in 2015, which reported that a lemongrass-oil tonic reduced dandruff over a two-week application period.

Note the binomial carefully, because most articles that cite this study get it wrong: the oil tested was from Cymbopogon flexuosus, East Indian lemongrass, not the culinary Cymbopogon citratus that you cook with and brew. The two species are close relatives with overlapping but not identical oil profiles. That is a real limitation on transferring the result, and it is the same genus-level sloppiness that produces the claim that lemongrass repels mosquitoes as citronella does — citronella oil comes mainly from C. nardus and C. winterianus.

Mechanistically the dandruff result is coherent: seborrhoeic dermatitis and dandruff involve Malassezia yeasts, lemongrass oil has antifungal activity, and a scalp is a surface where you can apply a real concentration. It is also a plausible-but-preliminary finding from a single small study, competing against well-established medicated shampoos (ketoconazole, ciclopirox, zinc pyrithione, selenium sulphide) that have far more evidence.

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Food Preservation and Household Use

Evidence tier: preliminary (in vitro and food-model). The most practically defensible application of lemongrass oil's antimicrobial activity is not in a person at all — it is in food and around the house, where the concentration is under your control and no absorption question arises.

• Food spoilage and preservation. Lemongrass oil has been studied extensively in food-science settings: in edible coatings and films, in active packaging exploiting its vapour-phase activity, and against spoilage moulds and foodborne pathogens on produce and in meat and dairy models. The limiting factor is usually flavour — a concentration that controls microbes often makes the food taste strongly of lemongrass. PubMed topic search.
• Mould in damp rooms. Vapour-phase antifungal activity underlies the use of lemongrass oil in household mould products. It is not a substitute for fixing the moisture source.
• Insect repellency. A formulated lemongrass-oil topical repellent gave meaningful but short-lived protection against mosquito bites in a study by Oyedele and colleagues in Phytomedicine in 2002. "Short-lived" is the key word: plant-oil repellents typically need reapplication every one to two hours, whereas DEET and picaridin last for hours. For genuine disease-risk situations, that difference matters.
• Surface cleaning. Reasonable as a pleasant-smelling adjunct; not a disinfectant with a validated kill claim.

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Why This Is Not an Antibiotic

It is worth being blunt, because this claim area causes real harm when misread.

1. No systemic evidence exists. There is no human study of lemongrass, in any form, treating a bacterial infection anywhere other than the mouth's surface. Zero.
2. The mechanism is non-selective. Membrane disruption at antimicrobial concentrations damages human cells too. This is why membrane-active agents make good antiseptics and bad systemic drugs.
3. Delay is the danger. Bacterial pneumonia, cellulitis, pyelonephritis, sepsis and dental abscess all get worse on the timescale of hours to days. Treating them with a plant oil while an infection advances is how a treatable illness becomes a hospital admission.
4. "Antibiotic resistance" is not a reason to substitute. Resistance is a genuine crisis and it is an argument for prescribing antibiotics correctly, not for replacing them with untested alternatives. Essential oils are being studied as adjuncts and as surface antimicrobials for good reasons; none of that research proposes them as systemic replacements.
5. Never inject, instil or douche with essential oil. These routes cause chemical injury and there is no scenario in which they are appropriate.

What lemongrass oil legitimately is: a broad-spectrum topical and environmental antimicrobial with a real laboratory record, a small amount of supportive human data for mucosal and skin surfaces, and a place in food preservation research.

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How to Use It Safely

Mouth rinse

The studied strength was 0.25% — a very dilute preparation. Commercially formulated products handle emulsification properly; oil and water do not mix, and a drop of neat oil floating on water delivers a concentrated hit to whatever mucosa it touches. Swish and spit. Never swallow. Stop if you get burning, ulceration or taste disturbance. This is an adjunct to brushing and flossing, not a replacement, and not a treatment for a dental abscess — that needs a dentist and usually an antibiotic.

Skin and scalp

Dilute in a carrier oil, conventionally to about 1–2% for general use, and patch-test on a small area for 24–48 hours first. Lemongrass oil is a documented irritant and contact allergen. Do not apply to broken skin, mucous membranes, or the eye area. Do not use on infants or young children.

Household and food

Follow the product's own directions for formulated repellents and cleaners. If you are using culinary lemongrass in cooking for its flavour and mild preservative effect, that is food use and needs no special caution.

Never

• Swallow lemongrass essential oil, in water, honey, capsules or anything else.
• Apply it neat to skin.
• Use it vaginally, rectally or in the ear canal.
• Use it instead of a prescribed antibiotic or antifungal.
• Leave the bottle within reach of a child, or diffuse it heavily around cats and dogs.

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Safety and Cautions

Skin. The dermatology reference is de Groot and Schmidt, Essential oils, part V: peppermint oil, lavender oil, and lemongrass oil, Dermatitis, 2016, which documents irritation and allergic contact dermatitis from lemongrass oil. Sensitisation is cumulative — someone who has used an oil for years without trouble can still become allergic to it.

Ingestion. There is no established safe oral dose of lemongrass essential oil and no reason to look for one. Concentrated essential oils cause mucosal injury and, in children, are a recognised cause of poisoning. The tea is a different matter and has a good safety record (see the Leite 1986 human trial, which found no toxicity from the infusion).

Pregnancy and breastfeeding. Lemongrass is traditionally treated as an emmenagogue. Culinary amounts are generally considered fine; the essential oil, strong daily medicinal teas and concentrated preparations are best avoided in pregnancy, and any regular medicinal use should be discussed with your obstetric provider. Do not use essential oils on or near infants.

High-dose citral. Animal work has reported prostatic hyperplasia in rats from repeated high-dose citral, attributed to an estrogen-like action — another argument against ingesting concentrated citral.

Children and pets. Concentrated essential oils are hazardous to small children if swallowed and can irritate airways. Cats in particular metabolise terpenes poorly. Store the bottle out of reach and ventilate diffused rooms.

Disclaimer. This page is educational and is not medical advice. The antimicrobial evidence for lemongrass is overwhelmingly in vitro; it does not establish that lemongrass treats any infection in a human body. Lemongrass is not an antibiotic or antifungal drug and must never be used in place of one. If you have signs of infection — fever, spreading redness, swelling, severe pain, difficulty breathing or swallowing, or a rapidly worsening illness — seek medical care promptly. Never swallow lemongrass essential oil.

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Key Research Papers

Citations resolve through PubMed topic searches rather than numeric identifiers. Evidence tier is stated for each — note how many read "in vitro."

1. Preliminary (in vitro). Naik MI, Fomda BA, Jaykumar E, Bhat JA. Antibacterial activity of lemongrass (Cymbopogon citratus) oil against some selected pathogenic bacteria. Asian Pacific Journal of Tropical Medicine, 2010. Find on PubMed
2. Preliminary (in vitro). Silva CB, Guterres SS, Weisheimer V, Schapoval EE. Antifungal activity of the lemongrass oil and citral against Candida spp. Brazilian Journal of Infectious Diseases, 2008. Find on PubMed — tested the whole oil and isolated citral side by side.
3. Preliminary (in vitro). Tyagi AK, Malik A. Liquid and vapour-phase antifungal activities of selected essential oils against Candida albicans: microscopic observations and chemical characterization of Cymbopogon citratus. BMC Complementary and Alternative Medicine, 2010. Find on PubMed
4. Preliminary (in vitro). Boukhatem MN, Ferhat MA, Kameli A, Saidi F, Kebir HT. Lemon grass (Cymbopogon citratus) essential oil as a potent anti-inflammatory and antifungal drug. Libyan Journal of Medicine, 2014. Find on PubMed
5. Preliminary (in vitro, resistant organisms). Warnke PH, Becker ST, Podschun R, et al. The battle against multi-resistant strains: renaissance of antimicrobial essential oils as a promising force to fight hospital-acquired infections. Journal of Cranio-Maxillofacial Surgery, 2009. Find on PubMed — lemongrass among the more active oils screened against resistant isolates.
6. Preliminary human (topical, oral candidiasis). Wright SC, Maree JE, Sibanyoni M. Treatment of oral thrush in HIV/AIDS patients with lemon juice and lemon grass (Cymbopogon citratus) and gentian violet. Phytomedicine, 2009. Find on PubMed — the only human infection study.
7. Preliminary human (small clinical, dental). A three-arm study of 0.25% lemongrass oil mouthwash against chlorhexidine and control, Journal of Clinical and Diagnostic Research, 2015. PubMed topic search: lemongrass oil mouthwash and chlorhexidine
8. Preliminary human (controlled, scalp). Chaisripipat W, Lourith N, Kanlayavattanakul M. Anti-dandruff hair tonic containing lemongrass (Cymbopogon flexuosus) oil. Complementary Medicine Research, 2015. Find on PubMed — C. flexuosus, not the culinary species.
9. Preliminary (in vitro, dental biofilm). PubMed topic search: Cymbopogon citratus, Streptococcus mutans and biofilm
10. Preliminary (in vitro, food science). PubMed topic search: lemongrass oil in food preservation and active packaging
11. Preliminary human (repellency). Oyedele AO, Gbolade AA, Sosan MB, Adewoyin FB, Soyelu OL, Orafidiya OO. Formulation of an effective mosquito-repellent topical product from lemongrass oil. Phytomedicine, 2002. Find on PubMed
12. Review (skin safety). de Groot A, Schmidt E. Essential oils, part V: peppermint oil, lavender oil, and lemongrass oil. Dermatitis, 2016. Find on PubMed
13. Reviews (overall). Shah G, et al. Scientific basis for the therapeutic use of Cymbopogon citratus, Stapf (lemon grass). Journal of Advanced Pharmaceutical Technology & Research, 2011. Find on PubMed · Ekpenyong CE, Akpan E, Nyoh A. Ethnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts. Chinese Journal of Natural Medicines, 2015. Find on PubMed
14. Context. Essential-oil mouthwashes for plaque and gingivitis: systematic reviews · chlorhexidine, the benchmark comparator

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Connections

• All Herbs
• Lemongrass Benefits Hub — all four deep dives and the themed research blocks.
• Lemongrass — botany, culinary use, compounds and overall safety.
• Tea Tree — the topical antimicrobial oil with the largest clinical literature.
• Clove — eugenol, the other great dental essential oil.
• Oregano — carvacrol and thymol, frequently compared with citral in the same screens.
• Thyme — thymol, a component of the classic essential-oil mouthwash.
• Cinnamon — cinnamaldehyde, another membrane-active food antimicrobial.
• Garlic — allicin, and the same in-vitro-versus-clinical gap.
• Oil Pulling — a related oral practice with similarly thin evidence.
• Gingivitis — the target of the mouthwash study.
• Periodontitis — why a rinse is never the whole treatment.
• Halitosis — masking versus treating.
• Dentistry — the oral health section.
• Staphylococcus aureus — the organism most often quoted in lemongrass screens.
• Escherichia coli — the Gram-negative comparator.
• Streptococcus pyogenes — a Gram-positive organism that needs real antibiotics.

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