Cracking at the interface between the fingernail and the flesh may be caused by onychomycosis, nail fungus disease, nail malnutrition, trauma and other reasons. 1. Inguinitis: may be due to Staphylococcus aureus, Streptococcus pyogenes, Candida albicans and other germs infection, triggered by inguinitis, and finger nail and meat interface cracking situation, usually accompanied by the inguinal local redness, swelling, pus, pain and other symptoms. 2. Nail fungal disease: commonly known as “gray nails”, is due to dermatophytes, yeasts and molds invade the nail plate and subnail tissues, can be manifested as nail discoloration, turbidity, thickening, atrophy, separation, warping and other symptoms. 3. Nail dystrophy: psoriasis, lichen planus, tumors, anemia and other diseases may lead to nail dystrophy, manifested as changes in nail morphology and structure, and may appear as cracks at the interface between the fingernail and the flesh. 4. Trauma: Trauma to the fingernail may lead to tearing of the nail and the muscle of the fingernail, and the symptoms of separation of the nail seam and the flesh, usually accompanied by bleeding, pain and other symptoms. Fingernail and flesh interface cracking may also be due to other factors, it is recommended that patients seek medical attention in a timely manner, under the guidance of the doctor for relevant examinations, in order to clarify the cause of the symptomatic treatment.