premature hair grey

What we call gray hair is either white or gray. Usually, it has turned this color due to a loss of melanin. But why do we get gray hair early?
Due to physiology or age, melanin in the body gradually decreases over time
Gray hair is considered premature in people under the age of 30.
Poliosis is grayness in localized areas of the hair, such as specific strands in the eye brows or eyelashes.
In addition, other people develop partial grayness, which are gray hairs spread out over the head.