Biotin (vitamin B7)
Genuinely essential for keratin production, genuinely useful in deficiency, and genuinely unsupported for hair growth in people who are not deficient.
What is biotin?
Biotin is a water-soluble B vitamin and an essential cofactor for carboxylase enzymes in fatty acid synthesis and amino acid metabolism, including pathways that produce keratin. Deficiency causes hair loss, brittle nails and dermatitis — which is where the hair and nail association originates.
The honest position
Biotin deficiency is rare in people eating an ordinary diet. Where it exists — from certain medications, malabsorption, or heavy raw-egg-white consumption — correcting it resolves the associated hair and nail problems, sometimes dramatically. That is a real and well-documented effect.
What does not follow is benefit from biotin in people who are not deficient, and the evidence for supplementation in that far larger group is weak. Most citations offered for biotin hair supplements are deficiency studies, which is a category error.
Topical biotin faces an additional problem: it is water-soluble and its established role is intracellular and metabolic, so a topical route is not the natural way to address a systemic cofactor. Evidence for topical biotin improving hair is thin.
One practical warning worth including
High-dose biotin supplementation interferes with a range of laboratory immunoassays, including thyroid and cardiac troponin tests, producing clinically misleading results. This has prompted regulatory safety communications. It is not a cosmetic issue, but it is the single most useful thing a reader of a biotin page can learn, and no brand page mentions it.
Where does biotin appear in the range?
Vegalab uses biotin in the Scalp Repair NanoSerum alongside panthenol, peptides and caffeine. As a supporting ingredient in a scalp formula that is reasonable; as the basis of a hair-growth claim it would not be.