Nail has a line is called nail longitudinal ridge, usually is the nail nutritional deficiencies caused by, and may also be pathological factors or chemical substances and other factors. 1. Nail malnutrition: most people’s nail beds are in a continuous state, when the patient’s nails have ridges, the most common reason is that the body lacks vitamins and trace elements, at this time the body to supply the growth of the nails is not enough nutrients, resulting in nail malnutrition. 2. Pathologic factors: lichen planus, chronic eczema, pemphigus, hypothyroidism and peripheral circulation disorders and other diseases can also be caused. 3. Chemical substances: the long-term use of certain pigments, solvents and osmotic agents in nail polish can damage the nail plate, resulting in brittle nails, nail longitudinal ridge and other damages. There may also be other causes of nail prongs, and it is recommended to go to the hospital to clarify the cause of the disease and standardize the treatment.