How Fast Does Hair Grow?

Hair Growth

Hair is a keratinized protein that is part of the integumentary system. Hair grows out of hair follicles embedded deep in the dermis. The only part of the hair that is alive is the root. The rest of the hair shaft is made up entirely of dead cells called keratin, which is a type of protein made up of long chains of amino acids. There are three different types of hair: terminal, vellus and lanugo. Terminal hair is the fully developed, thick, coarse hair found on the head, underarms and pubic area of humans. Vellus hair is the short, very fine hair also called "peach fuzz" that covers almost every part of the human body except the palms of the hands, soles of the feet, back of the ears, certain external genital organs and the lips. Lanugo hair is the hair that covers a fetus, and is also sometimes found on anorexics as their malnourished bodies struggle to retain heat.

Hair Growth

Hair generally grows an average of half an inch per month with growth predetermined by a person's genetic code. In a year, hair grows up to six inches. As a person ages, hair growth can slow down to a growth of about one-quarter inch per month. Cell division is responsible for the growth of hair. New hair cells form in the root and push the hair forward, making it longer. The new hair is always added at the root as the older hair inches downward slowly.
A strand of hair goes through three stages of growth during its life cycle. The first stage is known as the anagen. In this stage, new hair grows in the bulb of the hair follicle. The second stage is known as the catagen and it is the stage at which the hair cells in the bulb stop developing. The final stage is known as telogen, and it is when the old hair falls out and new hair starts to grow again. Hair grows at the same rate on every part of the head.

Other Factors

Few outside factors influence hair growth. The biggest external influence on the hair is stress. High levels of stress can cause hair loss and premature balding. The greatest influence on hair growth is a person's genes. Genetics determine the length, texture, thickness and color of a person's hair. There are no shampoos, conditioners or other hair care products that can influence the length of one's hair or make hair grow faster. Genetic code predisposes hair to only grow up to a certain length, and many people will find that their hair is incapable of growing past a genetically set point.