(1) Genetic factors are the main reason for the formation of freckles, not necessarily inherited from parents, but may be inherited after several generations. Generally speaking, freckles mostly appear on the face with whiter skin.
(2) When exposed to the sun, the ultraviolet rays in the sun stimulate frequent activities of the pigment cells under the skin and produce a large amount of melanin; on the other hand, it damages the normal metabolism of skin cells, so that the melanin cannot be discharged smoothly and remains on the skin. Even deposited in the dermis. Therefore, excessive sun exposure will aggravate and deepen freckles, but in winter, freckles will gradually fade.