There are many reasons for the appearance of vertical lines on the toenail, the vertical lines may be a normal physiological phenomenon, but may also be caused by external forces or disease: 1, physiological phenomenon: with the age of the human body began to aging, body function began to decline, the vertical lines on the toenail will grow more and more, the deeper, is a normal physiological phenomenon, no need to worry; 2, external trauma: toenail suffered from foreign objects, causing the capillaries under the deck Rupture, the toenail will sometimes have a black vertical lines, with the development of time, vertical lines will slowly disappear, this situation usually does not require special treatment; 3, chemical stimulation: If the toenail long-term exposure to chemical stimulation, or long-term use of nail polish, may lead to vertical lines on the toenail, you should avoid the use of nail polish, reduce chemical stimulation, usually the symptoms will also slowly ease; 4, blood supply Inadequate: When the body is in a state of fatigue, stress, anxiety or impaired liver and kidney function, the peripheral blood supply to the hands and feet is insufficient, poor blood circulation, it will lead to malnutrition around the toenail, when the toenail may produce vertical lines. Ensure sufficient sleep, pay attention to rest, moderate exercise, generally be able to recover; 5, nutritional deficiency: vitamin A involved in the formation of skin and toenail, when the body lacks vitamin A, iron and other trace elements will also lead to toenail abnormalities, if the hospital examination there is a lack of trace elements, timely supplementation of nutrition, such as zinc gluconate, etc., daily diet pay attention to supplemental protein, can improve the state of the toenail; 6, gray nail: That is, fungal infection, will cause the nail plate thickening, will produce vertical lines, color changes, toenail under the slag-like material, can be under the guidance of professional doctors, the use of antifungal drug treatment; 7, chronic liver disease: patients with liver disease will appear on the toenail black or brown vertical lines, if more than one toenail appears such a situation, should pay attention to the timely examination of liver function to clarify the diagnosis; 8, nail mother cell nevus: more presented as black lines on the toenail, which is a benign tumor with the possibility of malignant transformation, promptly go to the hospital for examination and treatment, and if necessary, take surgical treatment.