Vertical lines on nails may be caused by physiological reasons, malnutrition, protein deficiency, vitamin deficiency, nail fungus disease, skin diseases and other factors. 1. Physiological reasons: nails are flat and smooth, there will be uniform smooth fine lines, which is a normal physiological phenomenon. When with age, the water locking function of the nails will weaken, there will also be different degrees of vertical lines. 2. Malnutrition: If malnutrition occurs, it may affect the development of nails, resulting in the appearance of vertical lines on the nails. 3. Lack of protein: Keratin is the main protein that makes up the hair follicle and epidermis of the fur, when the body lacks protein, it will easily cause the nail epidermis to appear vertical lines. 4. Nail fungal disease: fingernail vertical lines may also be caused by nail fungal disease, nail plate infection caused by fungi, a skin disease, will be prone to fingernail vertical lines, horizontal lines, and so on, and even the color of the fingernail will change. 5. Skin diseases: If you suffer from psoriasis, lichen planus and other skin diseases, it may also lead to the appearance of vertical lines on the fingers. Finger nail vertical lines should go to the hospital in time, under the guidance of the doctor to carry out the appropriate treatment and therapy.