The appearance of black spots on the nails may be physiological, but also with pathological factors such as nail trauma, onychomycosis, melanoma and so on. 1. Physiological factors: nails local exogenous coloring caused by the nails themselves black spots, such as contact with chemicals or long-term outdoor work caused by hyperpigmentation, is a normal phenomenon but relatively rare. 2. Pathological factors (1) Nail trauma: such as nail trauma or extrusion, causing blood vessel rupture underneath the nail plate to form sub-nail bruises, manifesting as black spots on the nails, with the passage of time, the bruises will be gradually absorbed, and the black spots will also gradually disappear. (2) Onychomycosis: commonly known as gray nails, caused by fungal infection, the surface of nails can appear black spots, roughness and inequality symptoms, can also be accompanied by nails become empty, color change. (3) Pigmented nevus: it is related to the proliferation of melanocytes in the epidermis, and can grow in the nail bed and under the nail, and the local pigmentation can be increased and manifested as the symptom of black spots on the nails. If black spots appear on the nails, it is recommended to go to the hospital in time to find out the cause and then actively treat it to avoid delaying the condition.