Biotin shows up on almost every lash and brow serum label, plus a shelf of gummies and capsules. It's a real vitamin with a real, well-documented biological role — but "real vitamin" and "does something measurable for your lashes" are two different claims, and the second one deserves more scrutiny than a bottle label usually gives it. Here's what the research actually shows, including where it stops.
What biotin actually is
Biotin — also called vitamin B7 or vitamin H — is a water-soluble B-vitamin. The body uses it as a cofactor for enzymes involved in metabolising fats, carbohydrates and proteins, including the keratin protein that hair and nails are largely made of. That biochemical link to keratin is the entire reason biotin ended up in the hair-and-beauty aisle in the first place.
What the research says about biotin and hair
The evidence is more specific than the marketing. A literature review in the Journal of Clinical and Aesthetic Dermatology found that existing studies only support a benefit from biotin supplementation in a narrow set of situations: uncombable hair syndrome, short anagen syndrome, biotinidase and holocarboxylase deficiency, and cases of confirmed low biotin intake (for example, restrictive infant formulas or long-term IV nutrition). The review did not find a single randomised, placebo-controlled trial showing that biotin supplementation grows or thickens hair in generally healthy adults — and the highest-quality study it looked at found no difference between biotin and placebo at all.
The reason is straightforward: biotin only helps where there's a shortfall to correct. True biotin deficiency is rare — estimated at around 1 in 140,000 people — though a milder, subclinical shortfall may be somewhat more common in pregnancy, smokers and people on long-term antibiotics. If your levels are already adequate, which is the case for most people eating a varied diet, adding more biotin doesn't give hair anything extra to work with.
Does applying biotin topically do anything?
Most biotin research looks at oral supplements, not serums applied to skin — so it's worth asking separately whether a topical formula even reaches anywhere useful. Older percutaneous-absorption studies found that biotin in an ointment base is measurably absorbed through skin, raising blood biotin levels in both healthy volunteers and people with dermatitis. What's still genuinely unclear is what happens after that at the cellular level: researchers have noted there's surprisingly little study of exactly how skin cells take up and use biotin, given how widely it's used in cosmetic formulas. In plain terms: it can get into skin, but "gets absorbed" and "changes how a lash or brow hair looks" are not the same evidence, and we haven't seen a study that closes that gap.
Where that leaves a topical biotin serum
None of this makes biotin a bad ingredient to include — it's a mild, well-tolerated, water-soluble vitamin with a long history of cosmetic use, and it's cheap insurance for the small share of users whose diet or health situation leaves them mildly short on it. What it isn't is a growth stimulant. A biotin-containing serum applied to the lash line or brow doesn't influence the hair follicle or the growth cycle underneath the skin; at most, it's one of several ingredients supporting the condition and appearance of the hair that's already there. That distinction — conditioning existing hair versus changing how it grows — is the same line every cosmetic serum has to respect, and it's why we describe our own formulas carefully rather than promising more than a topical product can do.
Our Lash Serum lists Biotin on its full ingredient list alongside two conditioning peptides (Acetyl Tetrapeptide-3 and Biotinoyl Tripeptide-1), and describes it plainly as supporting "the appearance of thicker, healthier-looking lashes" — not lash growth. The Eyebrow Serum uses the same honest framing: biotin there "supports the appearance of fuller-looking, healthier-looking brows by conditioning the existing hair." Neither claim is about the follicle, and neither should be read as one.
Frequently asked questions
Does biotin make eyelashes or eyebrows grow?
The evidence doesn't support that. A review of the existing research found no randomised controlled trial showing biotin supplementation grows hair in people who aren't deficient, and the strongest available study found no difference from placebo. Biotin helps hair health in people with an actual shortfall — it isn't shown to add growth on top of a normal, adequate baseline.
Who actually benefits from taking biotin for hair?
People with a documented biotin deficiency or a condition affecting biotin metabolism (such as biotinidase deficiency), and people with an unusually low dietary intake — for example from certain restrictive formulas or long-term intravenous nutrition. True deficiency is rare; if you suspect one, that's a conversation for a doctor and a blood test, not a serum.
Is biotin absorbed when applied to skin, or only when taken orally?
Studies show biotin in a topical ointment is measurably absorbed through skin. What's not well studied is what skin and hair-follicle cells actually do with it once it's there, so "absorbed" shouldn't be read as "proven to change how hair looks or grows."
Is it safe to use a biotin-containing serum near the eyes?
Biotin itself is a mild, water-soluble vitamin with a long safety record in cosmetics. As with any new product, patch-test first and stop if you notice irritation — see our safety and usage page for full guidance.
Why does LashOriginals include biotin if the evidence is limited?
Because it's one part of a conditioning formula, not the whole claim. Our serums pair biotin with peptides and panthenol to condition the hair and skin that's already there, and we say so plainly rather than implying it drives growth — the same honesty that shapes our prostaglandin-free positioning across the range.
Browse: our conditioning lash and brow serums.
Related reading
- Prostaglandin-Free Lash Serums Explained: What the Ingredient List Actually Tells You
- Prostaglandin Lash Serum Side Effects
- Best Eyebrow Serum in Australia
- Do Lash Serums Work? A Realistic Look
Sources
- Journal of Clinical and Aesthetic Dermatology, Biotin for Hair Loss: Teasing Out the Evidence
- MDPI, Effectiveness of Biotin Supplementation for Hair Growth in Patients with Alopecia: A Systematic Review
- Journal of Nutritional Science and Vitaminology, Percutaneous Absorption of Biotin in Healthy Subjects and in Atopic Dermatitis Patients
- Journal of Investigative Dermatology, Transport of Biotin in Human Keratinocytes