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Question: How does hair turn color, such as from blonde to gray over the years?
Lexis, before answering your question, we first need to know why hair has color and why it differs from person to person (i.e. black, brown, blonde, red, gray, white, etc).
Hair is a filamentous biomaterial that grows from follicles found in the dermis (skin) and is mainly composed of protein. Simply put, hair is a silk-like material growing on the human body with its root, or follicle, under the skin.
Hair has color because the hair follicle produces something called "pigments" (which have nothing to do with a pig!). It is a colored biomaterial that can "paint" your hair.
There are two different kinds of pigment: eumelanin (black/brown color) and pheomelanin (pink/red color). What kind of color people will have is determined by their genes - people with more eumelanin will have black or brown hair and low amounts result in blond hair; people with more pheomelanin will have reddish hair. Most people have a mix of both, and different ratios result in different hair colors like blonde, red, etc.
As people age, the ability of their follicles to produce pigment decreases and they no longer have enough pigment to "paint" their hair, causing the hair color to become lighter, eventually turning gray or white. This change occurs over our whole body, not just the hair on our head. As people age, all of their hair eventually turns gray or white (but interestingly, in a certain order: first nose hair, then hair on the head, then beard, body hair and eyebrows!).
It's also important to note that aging is not the only cause of gray hair. Some conditions (such as albinism) are characterized by the complete or partial absence of pigments, usually due to defective genes. For those with albinism, their hair, skin and eyes (pigments also exist in our skin and eyes and are why we have different skin and eye colors) are all white or gray right from birth.
To sum everything up, people have different amounts of pigment in their hair, skin and eyes, which results in a variety of colors. Over time, our bodies lose the ability to create these pigment molecules, resulting in gray or white hair.
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