Nails on both sides of the long hard spines are mostly considered to be caused by the nail edge of the reverse peeling, the cause of which is mostly related to bad habits, mechanical damage and dry skin and other factors. 1. Bad habits: bad habits such as biting nails and tearing cuticles may also lead to localized damage, which may trigger the appearance of retrograde peeling of the nail margin. 2. Mechanical damage: If the nails and the surrounding skin are subjected to mechanical damage such as friction and trauma, it may induce the appearance of retrograde nail peeling. 3. Dry skin: If the water intake is low and the skin is dry, it may lead to dry skin, which may induce retrograde nail peeling. There is no single cause of retrograde nail peeling, so patients are advised to go to regular hospitals for relevant examinations to clarify the cause of the disease.