9 claims the marketing repeats
The hair-loss aisle runs on plausible-sounding mechanisms that were never tested end-to-end. We took the most common claims and graded each against the human evidence. None of these are graded on tone, only on trials.
Biotin corrects hair problems caused by biotin deficiency, which is rare. In people with normal levels, supplementation shows no measured regrowth benefit. The claim survives because the deficiency case is real and gets generalized to everyone.
Even if the active ingredient inhibits DHT in a dish, a shampoo's contact time with the scalp is a minute or two before rinse-off, far too brief to deliver a meaningful dose to the follicle. It fails on pharmacokinetics before efficacy is even in question. See how real topicals dose →
This rests almost entirely on a single 2015 trial with real methodological limits. It is worth tracking, not worth treating as settled. One study is a hypothesis, not a conclusion.
The evidence is a small self-reported study and a plausible mechanotransduction story. Harmless, possibly minor, but the causal claim outruns the data, which is the recurring pattern in this category.
Caffeine affects follicle cells in culture. Whether a rinse-off product delivers enough, long enough, to matter in a human scalp has not been shown. Cell-dish activity is a starting point, not proof.
Folk belief with no biological basis. A follicle produces one hair; plucking damages it, it does not multiply it. Included because it shows how confidently a claim can circulate with zero evidence.
Almost every myth here shares one flaw: a real mechanism in a dish is sold as a real result in a person, skipping the step where delivery, dose, and duration decide whether anything happens.
That gap is exactly why we grade on human trials, and why the interventions that clear the bar, and the frontier that might, are worth far more of your attention than the aisle.
