In an effort to answer a question posed this week...
TLC Style "Why does the hair on your arms stay short, while the hair on your head can grow very long?"A follicle will produce new cells for a certain period of time depending on where it is located on your body. This period is called the growth phase. Then it will stop for a period of time (the rest phase), and then restart the growth phase again.
Animals that shed have hair follicles that synchronize their rest phase so that all of the follicles enter the rest phase at once. This way, all of the hair falls out at one time. A dog that sheds will lose its hair in large clumps. Many animals can also switch the coloring agent in the hair follicle on and off -- so in the summer, the hair is pigmented brown with melanin (see How Sunburns and Sun Tans Work to learn about melanin), but in the winter it is not pigmented, leaving the hair white.
Thanks Nicolas.
