Graying of hair is a natural part of the aging process, and this affects all body hair, including the eyebrows. With most people, gray hair first appears on the scalp, but sometimes it is possible for gray hair to appear elsewhere too. Of course if the hair on your head is gray, your eyebrow hair will not be far behind.
Unless you are below the age of 30, there is nothing you can do to stop your hair from turning gray and in any case there is no cause for worry. Even if you are below 30, it is unlikely that you will be able to stop or reverse the process of graying. Premature graying of hair does unfortunately affect some people, and in many cases the cause is simply genetic.
You can however look into the possibility of there being some other cause. Smoking tobacco is thought to contribute to premature graying of hair, so if you smoke, this is one more reason to stop. You should also look at your diet carefully, and see if there could be any deficiency in any way, perhaps protein or minerals or vitamins. Finally, stress is a common cause of such problems, so try to minimize stress in your life.
answered by M W