Long freckles are caused by a lot of pigmentation, which is generally related to genetic factors, sun exposure or skin aging. 1. Hereditary factors: freckles are hereditary in family, if parents have freckles on face, the chance of their children having freckles is relatively high. 2. Sun exposure: sun exposure is an important factor in the formation of freckles. Prolonged exposure to ultraviolet rays outdoors will make the local melanocyte form larger and its ability to produce melanin stronger, leading to localized pigmentation. 3. Skin aging: with ageing, the metabolic function of the skin will gradually weaken, and the abnormal decomposition and metabolism of melanin particles will also lead to the aggravation of freckles. It is recommended to find a regular hospital for freckles and follow the advice of specialized doctors for standardized treatment to avoid adverse consequences.