Finger caps with vertical lines may be caused by nail malnutrition, lichen planus or eczema. 1. Nail malnutrition: due to the lack of certain vitamins, calcium, etc., affecting the function of the nail matrix cells at the root of the nail, resulting in abnormal synthesis of nail plate protein. After the structure of nail plate protein is changed, vertical lines may appear on the nails. 2. Lichen planus: Lichen planus under the nail destroys the normal structure of the nail, resulting in vertical lines on the fingernail. 3. Eczema: Periungual eczema may also destroy the normal structure of the nail, resulting in vertical lines on the fingernails. There may be other reasons for the vertical lines on the fingernails, when the vertical lines appear on the fingernails, you should go to the hospital in time to check, to make clear what kind of causes, and then carry out the corresponding treatment.