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 evaluates the efficacy of ingredients in trichological shampoos marketed for hair loss, identifying 112 ingredients from 43 shampoos. Only four ingredients—adenosine, caffeine, placental protein, and melatonin—were tested individually in clinical trials, showing moderate to low evidence of efficacy. Many ingredients were tested in complex formulations, making it difficult to attribute effects to specific components, and 20 ingredients lacked any clinical trial evidence. The review highlights significant gaps in scientific validation for many ingredients, emphasizing the need for more rigorous clinical testing to substantiate the claims of these shampoos.