The Centre, P.C. - Plastic Surgery Blog

A Primer on Human Hair - Wednesday, November 26, 2008

Although humans are considered "hairless" mammals, we are actually covered from head to toe with hair. It is called vellus hair and is fine and short so that we don't usually notice it. The hair we notice is terminal hair. A third type of hair is lanugo hair, which covers the body of a fetus but is mostly lost before birth. Hair is composed of dead cells -- if it were not, a haircut would be painful.

Structure of a Hair

Hairs consist of about 88 percent fibrous proteins called keratin. Keratin is also found in skin, teeth and nails, and in animal claws, hooves and tusks. It is a strong protein but can be either soft or hard. A hair grows from a hair follicle (its root) in the skin's middle layer, the dermis.

Each hair has:

• An outside cuticle which is translucent and consists of overlapping scales which cover the interior. Use of a hair conditioner after shampooing keeps these scales lying flat so the hair feels smooth.
• An interior core called the cortex or shaft, containing pigment granules (and some other structures). The pigment granules are small and solid and may vary in color within a single hair. They are clustered near the cuticle except in red hair, where they cluster in the center. They create melanin, the same substance which gives our skin its color.

Hair Growth

A normal scalp has between 100 and 150 thousand hairs though a blond head has more than either dark or red heads. Each hair is between 0.02 and 0.04 millimeter wide

Hairs grow at about a half-inch per month although that speed varies between individuals and can be affected by diet and by the seasons (faster in Spring and Summer). A healthy hair will live between two and six years and when it falls out a new one will start growing from that follicle. The lifetime of your hairs determines how long you can grow your hair -- whether you can have it be waist-length or even longer.

We have a total of about 1,400,000 hairs on our entire body. Men have about 30,000 in their moustaches or beards.

Hair Graying

As we age, the pigment granules in each hair gradually die out. That removes the hair's color, making it gray, silver or white. Any given hair may have scattered pigment granules remaining, making it partly gray and partly colored. The age at which our hair goes gray is hereditary.

Hair Removal

Laser hair removal is a very popular procedure. It is easiest done on dark hair with light skin. That is because the laser heat is absorbed by the pigment in the area. If the hair has little pigment, the laser is ineffective at removing it, and if the skin is strongly pigmented, the laser heat is absorbed there instead of in the hair.

Each person is individual in this respect, so please make no assumptions as to whether laser hair removal will work for you. Contact our cosmetic surgery office to set up a personal consultation and allow one of our doctors to examine your hair and skin.