Tuesday, June 20, 2006

What is Gray Hair (alopecia areata)

Prof Madiraju V Subramanyam

Hair typically turns gray as a result of aging. Pigment in the hair shaft comes from special cells at the root (base) of the hair. These cells are genetically programmed to make a certain amount of pigment (melanin) at specific ages. At some point in the aging process, these cells make less and less pigment until the hair has very little pigment. White hair has no pigment, and gray hair has some but not as much as a red, black or brown hair.Not all hairs respond in the same way or at the same time. So the graying process usually is gradual. You can`t prevent graying. Some people start graying in their 30s, and some not until their 60s. Genetics likely play a strong role in graying.

People rarely go gray overnight. If they do, it`s typically due to alopecia areata. This condition causes the thicker, darker hairs to stop growing before it affects the growth of gray hairs — giving the impression of graying overnight.

Alopecia areata eventually causes roundish patches of hair loss or complete loss of hair on the head or body. Its cause isn`t known.In red hair, nearly all the melanin is present in the form of phaeomelanin. Coloring red hair is difficult because of this different pigmentation, and bleaching red hair to a lighter shade is especially hard.Greying hairGray hair is one of the most familiar signs of aging. The age when greying starts depends on one`s genetic inheritance. But in half of all Caucasoid people, half the hairs on the scalp are grey by the age of 50.The loss of hair color is due to a gradual fall in melanin production in the hair bulb. If you look at the hairs on a greying head you find a full range of color, from the normal shade through to white along each hair, and also from one hair to another. Usually people notice their first gray hairs near their temples. Then the grayness spreads to the crown, and later to the back of the head.Rapid grayingYou have probably heard stories about people who are supposed to have `gone white overnight` following some terrible shock or grief. Treat these tales with caution!

A black hair cannot of itself suddenly turn white. Hairs grow for years with pigment inside them, and since they are `dead` there is no process by which the melanin throughout a hair can be naturally destroyed rapidly (although it may be bleached by sunlight over many years).Apparent rapid greying may be due to a selective shedding of pigmented hair in a person who has some gray hairs which are retained. Shedding of this kind usually takes several months, but can happen within a few days. If it does take place quickly the effects can be dramatic, since the person`s grey hairs may not have been at all obvious until the darker hairs were lost.Whether stress or shock can cause this kind of hair loss (known as alopecia areata) is unknown.

No comments: