Even experts cannot explain hair growth. It seems almost a magic process. And it takes great length's to stop it from growing. Just ask any women who has endured painful laser or electrolysis treatments to remove unwanted hair and yet it still comes back in many cases.
When it comes to optimal hair growth of existing healthy hairs an individuals general health, nutritional and stress factors are believed to be important.
Diets that do not provide adequate nutrition often cause hair loss. And alcoholics often have poor scalp hair because of malnutrition.
Vitamins and minerals are particularly important for hair growth. Zinc and the B vitamins are important for those individuals that may have a deficiency. A good daily multi-vitamin will provide both of these nutrients necessary for optimal growth.
MSM seems to be very important in hair growth, often speeding the process for many who take it.
The hair growth cycles is also influenced by the levels of various hormones in the blood. In male pattern baldness the scalp hair is most sensitive to the effects of male hormones and especially DHT. Men's hair growth is also affected by estrogen which slow down growth but extends the hair growth cycle. Women's Anagen or growth phase will typically be much longer than men's due to the effect of estrogen. And the hair will grow more slowly and with more thickness or diameter. Pregnant women often notice differences in hair growth due to large amounts of estrogen in the blood that overpowers the testosterone.