Do shampoos for thinning or hair loss actually regrow hair?

Verified-purchase reviewers of biotin and niacinamide shampoos like Nioxin System 2 and PURA D'OR frequently report fuller-looking, thicker-feeling hair, but those are cosmetic and volumizing effects. No over-the-counter shampoo is a substitute for clinically proven regrowth treatments, and the candidate data here did not include independent clinical testing to verify the brands' own 'clinically tested' claims.