References & Source Hierarchy
Every factual health or regulatory statement on this site traces to one of the sources below or to the current product label / vendor documentation. This hub lists the standing sources; individual pages cite their specific references inline.
Product and vendor documentation
- Kerassentials official product and sales page — formula presentation, ingredient list, pricing, bundles, bonuses, guarantee language, usage directions. Treated as vendor-reported; commercial facts re-verified and date-stamped (current verification: September 2026).
- Kerassentials order form (ClickBank checkout) — totals, payment methods, shipping presentation, guarantee badge. Vendor-reported.
- Vendor-published reference list — evaluated on our how it works page as context literature, not product proof.
U.S. government and regulatory
- U.S. National Library of Medicine / NIH — StatPearls, "Onychomycosis" (NCBI Bookshelf): disease prevalence, risk factors, nail biology, treatment tiers.
- NIH / NCBI literature (PubMed Central): ingredient-specific studies, including tea tree oil and nail-oil research.
- U.S. Centers for Disease Control and Prevention: antifungal resistance background; fungal infection public-health context.
- U.S. Food & Drug Administration: cosmetic vs. drug classification; cosmetic labeling guidance; dietary supplement labeling rules (21 CFR 101.36) used for the oral-vs-topical labeling contrast; facility registration vs. product approval distinctions.
- NIH Office of Dietary Supplements fact sheets (e.g., biotin, zinc, iron) for the nutrition articles.
Peer-reviewed literature cited on this site
- AbdelHamid D, Gomaa AH, Mohammed GF, et al. Evaluation of the therapeutic efficacy of tea tree oil in treatment of onychomycosis. Int J Pharmacogn Phytochem Res. 2017;9(12):1414-20.
- Alessandrini A, Starace M, Bruni F, et al. An open study to evaluate effectiveness and tolerability of a nail oil composed of vitamin E and essential oils in mild to moderate distal subungual onychomycosis. Skin Appendage Disord. 2020;6(1):14-8.
- Contact dermatitis and essential-oil safety literature (tea tree, citral/lemongrass, lavender allergenicity) as summarized on the side effects and safety pages.
How we weight them
The hierarchy and its rules — label first for identity, vendor for commerce, government and peer review for science, and the three-lane separation of fact/claim/evidence — are defined in the editorial policy. Two standing cautions govern every citation: a source must actually support the sentence it backs, and ingredient literature never upgrades to finished-product proof. Where the literature is thin, our pages say "thin."
Suggesting a source
Spotted a stronger or newer source for something we cite? The contact page welcomes it; corrections are checked and applied per policy.