Biotin

What it does

A B vitamin the body uses to process fats and proteins, including keratin. In shampoos it is mostly there to support “strengthening” claims.

Benefits

Taken by mouth it helps hair and nails in genuine biotin deficiency and a few rare conditions. There is no good evidence that it strengthens hair in healthy people, and none for use in a rinse-off shampoo.

Concerns & Risks

None well established for topical use. High-dose oral biotin supplements can interfere with some laboratory blood tests, so tell your doctor if you take them.