Melanocytes, cells found in the bottom layer of the epidermis, produce melanin, which is responsible for skin and hair color. The deciding factor that determines these colors is not how many melanocytes a person has but how active they are. For example, people who are albino have melanocytes, but since their activity is so low, no pigment is produced, giving them seemingly colorless features. In most people, there are around 2,000 melanocytes per square millimeter of skin, which surprisingly only covers roughly five percent of the cells in the epidermis layer.
These cells produce melanin after being triggered by environmental factors, such as spending time in the sun or around certain chemicals. However, if nothing triggers them, they will still replace melanin after a certain period of time. This process is called melanogenesis. When pigment is removed from the skin through improper use of a medical laser, melanogenesis ensures that the results are likely impermanent. As long as the melanocytes weren’t damaged during the laser removal treatment, they should be able to produce more melanin and return pigment to the skin.
In addition to being found in the lower layer of the epidermis, melanocytes can be found in the inner ear, the bones, the heart, the brain, and the spinal cord. It’s when these cells go dormant that people begin to experience graying of the hair and discolored skin.