The commonly held belief that age is the key factor in developing silver or gray hair is not strictly correct. There are, in fact, several potential causes of gray hair, including the levels of melanocyte cells in the hair, hereditary influences, and the level of vitamin B12 in the body. While it is true that age does play a part in the graying process, the alternative causes of gray hair mean that it can also occur in people during their teenage years.
Although it is referred to as "gray," during the graying process, the hairs are actually becoming transparent. Surrounding darker hairs give the appearance of a silver-gray coloring. Each hair follicle contains melanocyte cells, which produce pigment. This pigment will determine the natural color of the hair and maintain the color while the hair is growing.
The most prevalent pigment produced by the melanocyte cells in the hair follicle is melanin. A person's hair color is actually determined by the levels of melanin produced by the hair follicle; higher melanin levels produce darker hair. The failure of melanocyte stem cells (MSCs), resulting in a reduction in melanin levels, is one of the main causes of gray hair. As a person ages, the likelihood of the MSCs failing increases. This results in an elevated perception of age being related to gray hair.
Hereditary factors are also one of the causes of gray hair. Early onset graying — known as premature graying — occurring in a person's parents can invariably signify that the person will also begin to experience gray hair production at a relatively young age. In a way, this hereditary influence and the melanin production levels from the hair follicles are intrinsically linked.
A further occurrence linked as one of the causes of gray hair is the theory that a form of trauma can result in rapid graying of the hair. While it is true that people who have suffered an extreme shock can experience advanced graying, this effect is actually a result of a condition known as alopecia areata. This condition causes the hair to cease growing and eventually fall out. Darker hairs stop growing before the transparent hairs, which gives the appearance of rapidly graying hair.
An imbalance in the thyroid gland is one of the additional potential causes of gray hair. In addition to this, a general deficiency of vitamin B12 in the body can also reduce the levels of melanin being produced. While people with darker hair can appear to suffer more from graying, there is no direct link between natural hair color and the rate of graying.