Vertical lines on finger nails are usually caused by nail malnutrition, nail trauma and gray nails. 1. Nail malnutrition: If the patient has long been partial to food, picky eaters, anorexia, it is easy to lead to the lack of trace elements, which will have an impact on the growth of nails, thus leading to the appearance of vertical lines on the nails. 2. Nail trauma: Nail trauma can cause local growth abnormalities and vertical lines. 3. Gray nail: it is a disease caused by fungal infection of nails, which makes the nails become brittle and cracked, resulting in unevenness and vertical lines, and is contagious. If left untreated for a long time, it will not only infect other fingernails, but also others. Patients with the above symptoms, should go to the hospital in time, under the guidance of the doctor reasonable treatment.