Low vitamin D is linked with some types of hair loss, especially alopecia areata, but there is no good evidence that supplements help hair unless you are deficient. Ask a doctor about a blood test before you supplement.
technique to create small wounds in skin to activate collagen production and hair growth
Oil from the neem tree, used as a pesticide and in traditional remedies. Human evidence for hair or scalp benefits is limited; it can cause skin allergy and is poisonous if swallowed.
Prescription tablet (1 mg) that slowed hair loss versus placebo in two-year trials. Labels warn of sexual side effects that have continued after stopping, and of depression and suicidal thoughts; not for use in pregnancy.
A copper peptide used in cosmetics. Lab studies only; no human trial has tested it for hair loss or grey hair.