Hair color comes from cells in the hair follicle called melanocytes, which make pigment. Melanocytes don't live forever, and how well they give color to hair decreases over time. We see gray hair when the amount of pigment becomes less and white hair when all pigment has "run out" and is no longer made by the melanocytes. This usually happens later in life, with the average age between 35 and 50 years.

Poliosis is the name given when someone has a small patch of white hair. While this patch occurs most often along the forehead (so-called white forelock), it can involve hair anywhere on the body and can happen anytime in life. When healthy people have it, this simply means there is no pigment in the hair and skin of that involved area. Poliosis can also occur with medical conditions such as piebaldism, a genetic disease with single or multiple white patches of hair. In this case there usually are other family members with similar white patches of hair. Marfan's syndrome and Waardenburg's syndrome are other genetic disorders where this condition is noticed. Vitiligo is a skin condition that destroys melanocytes. This can affect the hair, but usually involves the skin as well. If your child also has white patches of skin, this may be vitiligo.

Since most cases of poliosis occur in otherwise healthy individuals, your 11-year-old's patch of white hair may be a normal type of poliosis from not having any pigment in that area. However, you should discuss this with your pediatrician, since there can be some genetic disorders and other associated findings with poliosis. If there is strong concern, your child may need a further evaluation, including a thorough skin exam, detailed family history, eye examination, and possible blood testing.