Freckles are mainly caused by genetic factors and sun exposure, in addition, human race and living habits can also lead to the occurrence of freckles. 1. Genetic factors: Freckles is an autosomal dominant disease with family aggregation. Generally speaking, if one of the parents suffers from freckles, the incidence rate of the children may be 1/2, while if both parents have freckles, the incidence rate of the children may be 3/4. 2. Sun exposure: sun exposure can induce or aggravate the occurrence of freckles. Excessive sun exposure will lead to the enlargement of melanocytes in the skin and enhance the ability of melanocytes to produce melanin, thus leading to the enlargement, deepening and increase of freckles. 3. Ethnicity: Generally, people with light skin color are more likely to develop freckles, so white people are more prone to freckles, especially white people with light or red hair. 4. Lifestyle habits: Bad lifestyle habits may aggravate freckles, such as staying up late at night, failing to clean up after putting on make-up, facing electronic screens for a long time, and so on. Patients with freckles are recommended to go to regular hospitals for consultation and standardized treatment under the guidance of specialists.