Hair grows all over your body, with a few exceptions (including your lips, palms, and soles of your feet), and the average person has about 5 million hairs, most of which grow for between two and six years before falling out and being replaced. Hair — especially the hair on your head — can be a good indicator of your overall health.

Although there are huge variations in what's normal and healthy when it comes to hair (some people have hair that's thicker, curlier, or longer than others), a healthy head of hair is generally shiny, lively, and full. The living parts of the hair — the root, the follicle that contains it, and the sebaceous (oil) gland that's attached to it — are beneath the surface of the skin. The part that's visible, the shaft, which is covered by a cuticle, is dead. Hair gets its color from melanin — the more melanin, the darker the hair. Loss of melanin results in gray or white hair.

Healthy hair requires a few things to stay that way: a good diet with plenty of protein and fat (essential for hair, skin, and other tissues), sufficient sebum, or oil that's produced in the scalp (enough to coat and protect the hair shaft, but not so much that it builds up or collects excess dirt), and a healthy balance of hormones. The good news is that many herbs — whether incorporated in commercial products or used au naturel — can keep your hair healthy without all the synthetic ingredients.