What the literature supports for each formulation class

A hair and scalp protocol draws on formulation classes with very different evidence behind them, from an FDA-approved oral label to follicle culture and small early trials (Fig. 1). These references take each class on its own terms: what the studies were, what they reported, and what the regulators have said, with the study design labeled beside every citation.

Written for licensed practitioners and practice operators. Two product regimes appear here and never mix: exosome material is supplied for topical aesthetic use, and compounded scalp formulations are 503A prescription products. Neither is FDA-approved for hair loss.