Freckles is a common autosomal dominant disorder. It mostly occurs in females and appears from about 5 years of age, increasing in number with age and reaching a peak at puberty. The disease usually occurs on the exposed facial skin, but rarely on the back of the hands, forearms and neck. The lesions are numerous, generally 1.0-4.0 mm round, oval or polygonal, with irregularly shaped light to dark brown patches. The histopathology shows that the melanin content of the basal layer of the epidermis is increased, but the number of melanocytes does not increase, but the cytosol is larger, with more and longer dendritic protrusions, and the number of melanin vesicles in the cytoplasm is increased. Freckles are characterized by seasonal changes, i.e. aggravated in summer and reduced in winter. Previous treatments for freckles include phenol, trichloroacetic acid, chemical peeling such as herbal crystal cream and liquid nitrogen freezing treatment, but there are poor selectivity, difficult to control the depth and easy to lead to scar formation.