Background: Biotin (vitamin B7) is widely marketed and used as an over-the-counter supplement for hair, skin, and nails, despite uncertainty about its clinical benefit for alopecia and hair growth. While overt biotin deficiency can be associated with hair changes, clinically meaningful deficiency is uncommon in individuals consuming a balanced diet, and published findings on biotin status in hair loss populations are inconsistent. Methods: This is a systematic review following PRISMA. A search was conducted in PubMed/MEDLINE (PROSPERO: CRD420251274919) for human studies evaluating biotin (alone or in combination) and including hair outcomes. The synthesis was qualitative due to clinical and methodological heterogeneity. Results: Ten studies were included. Across controlled and quasi-experimental interventions, biotin monotherapy did not show consistent benefit on objective hair growth outcomes; when improvements were reported, they typically occurred in combined regimens and were difficult to attribute specifically to biotin. Studies showed mixed findings on “low” biotin levels in hair loss populations, whereas controlled studies in telogen effluvium found no significant differences in serum biotin versus controls. No serious adverse events attributable to biotin were identified; however, high-dose biotin may interfere with immunoassays, potentially leading to clinically relevant false laboratory results. Conclusions: Current evidence does not support routine biotin supplementation for alopecia in the absence of documented deficiency, although it may be considered in scenarios with risk or confirmation of deficiency/malabsorption.
Moltó-Balado et al. (Mon,) studied this question.