Age spots are also called seborrheic keratosis, the cause of which has not been fully clarified and is mainly seen in adults over 40 years of age. age spots appear at 40 years of age and are considered to be related to heredity, skin tigers, air pollution and other factors. 1. Genetic factors: Seborrheic keratosis multiforme has certain genetic susceptibility, and patients often have family history of the disease, and age spots may appear on the skin in their 40s. 2. Skin aging: the incidence of seborrheic keratosis increases in adults over 40 years old, and seborrheic keratosis is associated with aging skin. 3. Air pollution: airborne pollutants in contact with the skin can also accelerate skin aging and age spots. There may be other reasons for age spots at 40 years old. If you feel that it affects your aesthetics, treat it by laser, freezing or surgical excision if necessary.