Demodex folliculorum is not a fringe pathogen. Nearly every adult human carries colonies of these mites in facial follicles, where they feed on sebum and shed skin cells, and in most people they cause no harm at all. Problems arise when populations expand beyond normal levels, a condition known as demodicosis, which is increasingly recognized as a driver or aggravating factor in rosacea, blepharitis, perioral dermatitis, and other chronic inflammatory conditions. Overgrowth has been linked to immune dysregulation, bacterial proliferation within the mites, and disruption of the follicular environment. Topical ivermectin one percent remains the best-characterized treatment, but clinicians have reported refractory cases in which mites persist despite repeated courses, and the drug’s price places it out of reach for many patients in low- and middle-income countries. That therapeutic gap is precisely what motivated Anon Paichitrojjana of the School of Anti-Aging and Regenerative Medicine to systematically screen lemongrass preparations against the mite.

The experimental design was deliberately comparative. Mites were harvested from residual material on standardized skin surface biopsy slides, a routine diagnostic technique in which cyanoacrylate adhesive is used to extract follicular contents from the skin of patients being evaluated for demodicosis and rosacea. Because the study used only leftover diagnostic specimens, the Mae Fah Luang Ethics Committee on Human Research waived the requirement for written informed consent, judging the work minimal risk, and the protocol was approved under the principles of the Declaration of Helsinki. Ten mites were assigned to each of nine test agents: lemongrass essential oil alone, lemongrass ethanolic extract alone, a three-part mixture of essential oil, extract, and ninety-five percent ethanol in a one-to-one-to-one ratio, a second three-part mixture replacing the ethanol with PEG-40 hydrogenated castor oil in a one-to-one-to-zero-point-five ratio, ivermectin one percent, ethanol alone, PEG-40 alone, essential oil diluted in immersion oil, and immersion oil as the negative control. Survival was tracked microscopically, with mites considered dead when they showed no movement.

The results were unambiguous. All mites exposed to any of the active test agents died within forty-four minutes, whereas mites suspended in immersion oil, the inert control, remained alive for more than two hundred forty minutes of observation. The two combined lemongrass formulations, the essential-oil-plus-extract mixtures containing either ethanol or PEG-40, produced the shortest survival times of any agent tested under the study conditions. Notably, ninety-five percent ethanol on its own also demonstrated substantial acaricidal activity, a detail that matters enormously for interpreting the data, because it means the ethanol vehicle in the combination formulations cannot be assumed to be biologically inert. Ivermectin one percent, included as a reference agent, killed mites within the same overall window, confirming that the assay could detect clinically meaningful acaricidal activity.

What makes lemongrass lethal to a mite? The chemistry of Cymbopogon citratus offers plausible mechanisms. Lemongrass essential oil is dominated by citral, a mixture of the isomeric aldehydes geranial and neral, which are known to disrupt insect and arachnid cell membranes and interfere with mitochondrial respiration. Essential oils in general act as neurotoxicants and membrane disruptors in arthropods, and their lipophilic constituents penetrate the cuticle readily. The ethanolic extract, by contrast, contains a broader and less volatile profile of compounds, including phenolic acids and flavonoids, which may contribute oxidative stress or additional membrane damage. The logic of combining the essential oil with the extract is that the two preparations deliver complementary phytochemical payloads, while the ethanol or PEG-40 component serves as a solubilizer that keeps the hydrophobic oil dispersed and may itself enhance penetration of active compounds into the mite’s protective cuticle.

The inclusion of PEG-40 hydrogenated castor oil is particularly interesting from a formulation science perspective. Ethanol is an effective solvent but a well-known skin irritant and drying agent, especially problematic for patients whose skin barrier is already compromised by rosacea or demodicosis. PEG-40 hydrogenated castor oil is a nonionic surfactant and solubilizer widely used in cosmetics precisely because it can disperse essential oils in aqueous formulations while being far gentler on the skin. The fact that the PEG-40-containing lemongrass formulation matched the ethanol-containing version for speed of kill suggests that a less irritating vehicle could achieve equivalent acaricidal performance, which would be a meaningful advantage if these laboratory findings ever translate into a topical product for inflamed, sensitive facial skin.

The author and the journal are appropriately cautious about what the study does and does not show. This was an in vitro assay on mites removed from their follicular habitat, observed in small numbers, ten per agent, under artificial conditions. The skin surface biopsy environment is not the same as a living follicle, where mites burrow head-down in sebum, protected by host tissue, and where a topical agent must penetrate the follicular opening and the mite’s cuticle simultaneously. The study itself acknowledges that further work is needed to clarify the individual contributions of each component, since the combination design means the observed effect cannot yet be attributed to citral, the extract’s phenolics, the ethanol, or the surfactant acting alone or in synergy. Safety, formulation stability, and clinical efficacy all remain untested, and the author explicitly frames the findings as support for further investigation rather than a treatment recommendation.

Those caveats notwithstanding, the study arrives at a moment of genuine unmet need. Demodex-associated dermatoses are chronic, relapsing, and psychologically burdensome, and treatment options beyond ivermectin are limited. Tea tree oil, the other botanical agent with documented demodicidal activity, has been formulated into commercial cleansers and eyelid wipes, but it too can cause irritation and allergic contact dermatitis in a subset of patients. A lemongrass-based alternative with rapid killing kinetics would add a second botanical option and potentially allow combination or rotation strategies for resistant cases. The open-access publication, funded by publication charges from Mae Fah Luang University with no external funding for the research itself and no competing interests declared, makes the full methods available to any laboratory wishing to replicate or extend the work.

The next steps are well defined by the field’s standard progression. Follow-up studies would need to isolate and quantify the active constituents, likely using gas chromatography-mass spectrometry to characterize the essential oil and high-performance liquid chromatography to profile the extract, then test purified citral and other candidates individually to establish dose-response relationships and minimum lethal concentrations. Formulation stability testing, preservative challenges, and ocular safety assessment would be essential for any product intended for the eyelid margin, where Demodex blepharitis is common. Ultimately, randomized clinical trials comparing a lemongrass formulation against vehicle and against ivermectin in patients with confirmed demodicosis would determine whether the forty-four-minute laboratory kill translates into real-world clearance of mites and resolution of inflammatory disease. Until then, the study stands as an intriguing proof of concept: a humble culinary herb, rigorously tested, outpacing a pharmaceutical standard in the petri dish.

Subject of Research: In vitro acaricidal activity of lemongrass preparations against the human follicle mite Demodex folliculorum

Article Title: Comparative in vitro acaricidal activity of lemongrass preparations and selected formulations against Demodex folliculorum

Article References: Paichitrojjana, A. (2026). Comparative in vitro acaricidal activity of lemongrass preparations and selected formulations against Demodex folliculorum. BMC Complementary Medicine and Therapies. https://doi.org/10.1186/s12906-026-05591-0

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05591-0

Keywords: Demodex folliculorum, lemongrass essential oil, Cymbopogon citratus, demodicosis, rosacea, acaricidal activity, ivermectin, essential oil, topical formulation, in vitro assay, natural products, dermatology