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Evidence rating: Moderate — the active ingredients have randomized trials against nail fungus, but head-to-head testing shows they penetrate the nail poorly
What Kerassentials Claims To Be
Kerassentials is a brush-on oil sold for nail and skin health, aimed at discoloured, thickened, brittle toenails — the visible signature of onychomycosis. Unlike most supplements covered on this site, it is a topical, which changes the analysis entirely. Absorption is not about digestion; it is about whether the ingredients can cross the nail plate, which is a dense keratin barrier that has defeated better-funded formulations than this one.
What’s Actually In It
Eight named ingredients, no disclosed concentrations:
- Undecylenic acid — the only FDA-recognised topical antifungal in the blend
- Tea tree oil (Melaleuca alternifolia)
- Lavender oil
- Lemongrass oil
- Organic flaxseed oil
- Almond oil
- Aloe vera
- Tocopheryl acetate (vitamin E)
Four of those — flaxseed, almond, aloe, vitamin E — are carriers and conditioners rather than antifungals. The active claim rests on undecylenic acid and the three essential oils.
Concentration matters enormously here, and it is not published. The undecylenic acid products tested in the literature below were 25% solutions.
What The Research Shows
According to PubMed, tea tree oil has been tested for exactly this indication, twice, with instructive results.
Tea tree oil matched a prescription antifungal — but both performed modestly. A double-blind, multicentre, randomized controlled trial enrolled 117 patients with culture-proven distal subungual onychomycosis and assigned them twice-daily 1% clotrimazole solution or 100% tea tree oil for six months. At six months the groups were comparable: culture cure of 11% (clotrimazole) versus 18% (tea tree oil), with partial or full clinical resolution in 61% and 60% respectively. Three months later about half of each group reported continued improvement. PubMed Read that carefully — a culture cure rate of 18% means the fungus was actually eradicated in fewer than one in five people, even as most reported the nail looked better.
A combination trial produced far better numbers, but the drug did the heavy lifting. A randomized, double-blind, placebo-controlled study put 60 patients on a cream containing 2% butenafine hydrochloride plus 5% Melaleuca alternifolia oil, or placebo. After 16 weeks, 80% of the active group were cured versus none on placebo, with no relapses during follow-up. DOI This is a genuinely impressive result, but butenafine is a pharmaceutical antifungal. The trial does not isolate what tea tree oil contributed.
Lavender oil kills fungus in a dish. Testing of Lavandula viridis essential oil against pathogenic fungi found dermatophytes among the most sensitive organisms, with minimum inhibitory concentrations equal to minimum lethal concentrations — indicating a fungicidal rather than merely inhibitory effect — and flow cytometry pointing to membrane disruption as the mechanism. The authors were direct that “clinical trials are required to evaluate the practical relevance of our in vitro research.” DOI
Here is the finding that cuts hardest against this product. An ex vivo study compared seven topical antifungals — three prescription products and four over-the-counter tolnaftate and/or undecylenic acid 25% solutions — for their ability to penetrate human cadaver toenails and inhibit Trichophyton rubrum and T. mentagrophytes. Applied to keratin-free discs, the OTC products performed respectably. Applied to actual nails, they did not: zones of inhibition for the OTC group ranged from 10.5 to 34.2 mm, versus 82.1 mm for prescription efinaconazole and 63.5 mm for tavaborole (all p \< 0.001). DOI The active ingredients work; getting them through the nail is where OTC formulas lose.
A dermatology review reaches a compatible conclusion. Reviewing the laboratory data and clinical studies on over-the-counter and natural onychomycosis remedies, the authors note that FDA-approved topicals themselves have incomplete efficacy compared with oral agents and require long treatment courses — which is precisely why interest in OTC alternatives persists. PubMed
The Honest Verdict
What holds up: These are not invented ingredients. Undecylenic acid is a recognised topical antifungal. Tea tree oil has two randomized controlled trials specifically in toenail onychomycosis, one of which put it on par with a prescription topical. Lavender oil has credible in vitro antifungal activity against dermatophytes. As a category, this is better supported than most cosmetic nail products.
What doesn’t: The cure rates. In the cleanest tea tree oil trial, 18% achieved culture cure after six months of twice-daily application — meaning roughly four in five did not. And the 2024 penetration study is a direct, hard-to-argue-with problem: OTC undecylenic acid formulations delivered a fraction of the antifungal activity through real nail that prescription options did. Kerassentials publishes no concentrations, so it cannot even be positioned relative to the 25% solutions that were tested. Anyone promising rapid clearance from a brush-on oil is promising something the literature does not deliver.
Who this makes sense for: Someone with mild, early, cosmetically annoying nail discolouration who wants to try a low-risk topical before escalating; someone maintaining a nail after successful treatment; or someone who cannot take oral antifungals because of liver concerns or drug interactions and has discussed topicals with a clinician. Expect months, not weeks, and pair it with regular debridement — every trial above included nail trimming and filing as part of the protocol.
Who should skip it: Anyone with a thick, painful, or extensively involved nail; anyone with diabetes or peripheral vascular disease, where foot infections are a genuine clinical risk; and anyone who has not had the diagnosis confirmed. Roughly half of dystrophic-looking nails are not fungal at all, and applying antifungal oil to psoriasis or trauma damage does nothing.
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This article is for informational purposes only and is not medical advice. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. These statements have not been evaluated by the Food and Drug Administration. Talk to your physician or podiatrist before starting any treatment, especially if you have diabetes, circulatory problems, or a diagnosed condition.
Research cited via PubMed:
- Buck DS, et al. J Fam Pract. 1994;38(6):601-5. PubMed
- Syed TA, et al. Trop Med Int Health. 1999;4(4):284-7. DOI
- Zuzarte M, et al. J Med Microbiol. 2011;60(Pt 5):612-618. DOI
- Elabbasi A, et al. Dermatol Ther (Heidelb). 2024;14(9):2495-2507. DOI
- Halteh P, Scher RK, Lipner SR. Cutis. 2016;98(5):E16-E25. PubMed