Split nail edges may be related to genetics, onychomycosis, and vitamin deficiencies. 1. Heredity: If the split is on the little toe, it is known as a flap nail, which may be an autosomal dominant trait and is generally associated with heredity. 2. Onychomycosis: It is mainly caused by dermatophyte infections, followed by yeasts and other bacteria. It can lead to pitting or irregular sheet-like breakage of nails with uneven surface. 3. Vitamin deficiencies: Vitamin A, for example, can cause roughness of the skin when it is deficient, accompanied by thin, brittle nails that are prone to furrowing and may have split edges. Nail edges can also be seen in other causes, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions to carry out relevant examinations, with the help of the doctor to clarify the cause, and targeted treatment or treatment.