There are many reasons for dark spots on the body, such as post-inflammatory hyperpigmentation, pigmented nevus, seborrheic keratosis and so on. 1. Post-inflammatory hyperpigmentation: post-inflammatory hyperpigmentation is a secondary change, which is due to many kinds of skin diseases, such as dermatitis, papular urticaria, eczema, etc., which leave hyperpigmentation on the body after the skin diseases are cured, thus leading to the phenomenon of long dark spots on the body. 2. Nevus pigmentosus: Nevus pigmentosus is a benign tumor of pigment cells, the cause of which is not yet clear, and it can show the phenomenon of black spots, black papules, etc., which is usually not accompanied by other uncomfortable symptoms. 3. Seborrheic keratosis: seborrheic keratosis is common in middle-aged and old people, which can show black macules and brown macules with rough surface, usually without obvious conscious symptoms, and may be related to age, ultraviolet radiation, heredity and other factors. There are many reasons that lead to black spots on the body, if the black spots on the body gradually increase, it is recommended that patients go to the hospital in time to improve the examination, a clear diagnosis, and take targeted treatment in a timely manner, and do not ignore the symptoms and take it lightly.