Yes, biotin can be absorbed through the skin. A study published in the Journal of Nutritional Science and Vitaminology tested biotin-containing ointment on both healthy volunteers and people with atopic dermatitis, and found that applying it to the skin raised blood biotin levels in both groups. That said, the amount absorbed topically is modest compared to what you’d get from an oral supplement, and the practical benefits of biotin-containing skincare products remain limited by thin evidence.
Why Biotin Passes Through Skin
One key factor in whether a substance can penetrate skin is its molecular size. Molecules under 500 Daltons generally pass through the outermost skin barrier, called the stratum corneum. Biotin has a molecular weight of about 244 Daltons, well under that threshold. This relatively small size allows it to slip between the tightly packed cells of the skin’s surface layer and reach deeper tissue.
Once biotin reaches living skin cells, it doesn’t just sit there passively. Research published in the Journal of Investigative Dermatology found that human keratinocytes (the main cell type in the outer skin layer) have dedicated transport systems that actively pull biotin inside. These transporters are sodium-dependent, meaning they use the body’s natural sodium gradient as an energy source. The study identified both a general vitamin transporter and a second, extremely high-affinity system with strong specificity for biotin, suggesting skin cells are well-equipped to take it up.
What the Human Evidence Shows
The most direct evidence comes from that Japanese study measuring blood levels before and after applying biotin ointment. In healthy subjects, average serum biotin rose from about 41.5 to 50.2 nmol/L. In atopic dermatitis patients, who started with lower baseline levels (27.9 nmol/L on average), the increase was more pronounced, reaching about 50.7 nmol/L. The researchers concluded that biotin is “readily absorbed” through both normal and inflamed skin, and that people with initially low levels may benefit the most from topical application.
That’s a meaningful finding, but context matters. The increase in healthy subjects was roughly 21%, and the ointment used was a controlled formulation designed to stay on the skin. This doesn’t automatically translate to every biotin-containing product you’d find at a drugstore.
Topical vs. Oral Biotin
Oral biotin supplements deliver the vitamin directly to the gut, where it’s absorbed into the bloodstream in larger quantities than what skin application provides. However, oral biotin has its own limitations. It has low solubility in water and common pharmaceutical solvents, which can reduce how much your body actually absorbs from a capsule or tablet. This is one reason some product developers have explored topical delivery as an alternative route.
For someone with a genuine biotin deficiency (which is rare in otherwise healthy adults), oral supplementation is still the standard approach and delivers far higher systemic levels. Topical biotin is better understood as a way to deliver the vitamin locally to skin cells rather than as a replacement for oral intake.
Do Biotin Skincare Products Actually Work?
Here’s where the science gets thinner. Biotin appears in shampoos, serums, moisturizers, and scalp treatments, often marketed for hair growth or skin repair. But the absorption evidence above comes from ointments left on the skin, not rinse-off products like shampoos that stay in contact with your scalp for a minute or two. Contact time matters for absorption, so a biotin shampoo is far less likely to deliver meaningful amounts than a leave-on cream.
The evidence for biotin improving hair growth in people who aren’t deficient is particularly weak. A review published in Skin Appendage Disorders found that biotin does not influence the growth or development of normal hair follicle cells in lab studies. And a survey of physicians published in Medicina noted that no randomized controlled trials have demonstrated biotin helps with dermatological conditions. Biotin does appear in cosmetics for dry, oily, or irritated skin, where it’s thought to support sebaceous gland function, but rigorous clinical data backing these claims is largely absent.
The medical consensus is essentially this: biotin remains understudied for skin, hair, and nail benefits. Some patients report improvements and continue using it based on personal preference, but the science hasn’t caught up to the marketing.
When Topical Biotin Might Make Sense
The strongest case for topical biotin is in people with low baseline biotin levels or compromised skin barriers, like those with eczema or atopic dermatitis. The absorption study showed that these individuals had a larger relative increase in blood biotin after topical application. If you’re using a leave-on product (a cream, ointment, or serum rather than a shampoo), you’re giving the biotin more time to cross the skin barrier.
If you’re considering a biotin-containing topical product, look for leave-on formulations and keep expectations realistic. The vitamin does absorb through skin, and skin cells do actively transport it. But the leap from “it gets into skin cells” to “it visibly improves your hair or complexion” is one the research hasn’t firmly made yet for people with normal biotin levels.