Nail splitting may be caused by fungal infection, malnutrition or trauma. 1. Fungal infection: Fungal infection can make nails thin and deformed, easy to break, usually showing a dark yellow color different from the normal transparent color, you can go to the hospital to do fungal immunofluorescence test to further clarify whether it is a fungal infection. 2. Malnutrition: due to the lack of trace elements or vitamins, the nails will be more fragile, which will easily lead to nail rupture and deformation, and the situation of nail splitting. 3. Trauma: it may be due to contact with chemical substances that corrode the nails, making them thin, layered and prone to splitting, or contact with hard objects that damage the nails and lead to nail splitting. There may be other reasons for splitting nails, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease.