Ingredients of Trichological Shampoos with Alleged Beneficial Effects on Hair: What Is Really Known About Their Efficacy? A Scoping Review of an Area with More Unknowns Than Knowns

This scoping review investigates the efficacy of ingredients in trichological shampoos advertised as active against hair loss. Out of 112 ingredients identified in 43 shampoos, only 16 were tested in 29 clinical trials. Caffeine, adenosine, placental protein, and melatonin were individually tested, each showing moderate evidence of efficacy. However, 12 other ingredients were only tested in complex formulations, making it difficult to attribute effects to specific components. No clinical trials were found for 20 ingredients frequently claimed to be active. Overall, the evidence supporting the efficacy of these ingredients is limited, highlighting significant gaps in the scientific validation of non-prescription hair loss treatments.