Gray or white hair — sometimes colloquially called "salt and pepper" when it is 'peppered' throughout dark hair — is not caused by a true gray or white pigment, but is due to a lack of pigmentation and melanin. The clear hairs appear as gray or white because of the way light reflects from the hairs. Gray hair color typically occurs naturally as people age (see "Effects of aging on hair color", below). For some people this can happen at a very young age (for example, at the age of 10). The same is true for white hair. In some cases, gray hair may be caused by thyroid deficiencies, Waardenburg syndrome or a deficiency of B₁₂.^[9]