Empty toenails are usually nail separations, which is a gradual separation of the nail plate from the free edge and the nail bed without shedding. It is mainly caused by psoriasis, chemical factors and gray nails. 1. Psoriasis: it is a kind of skin disease caused by the interaction of environmental factors, genetic factors, immunological factors and other factors. When the patient develops pustular psoriasis, the nail is often involved, which can be punctate depression, transverse groove, nail separation, and pus accumulation under the nail. 2. Chemical factors: when the patient long-term local external chemical agents, such as solvents, insecticides, cosmetics containing phenol or formalin. It can make the nail appear lesions, thus causing nail separation. 3. Gray nail: due to the lesions caused by fungal invasion of the nail plate, can make the nail structure change, color change, etc., which can appear nail deformation, thickening, detachment, separation and so on. It is recommended that patients with nail separation go to the hospital in time and follow the doctor’s instructions for treatment to avoid delaying the condition.