Nail cap with horizontal grooves can be caused by malnutrition, aging, nail fungus disease and other factors. 1. Malnutrition: Trauma to the nail cap or lack of micronutrients due to partial diet, or chemical stimulation of the nail cap due to long-term use of nail care products, disinfectants, detergents, etc. can lead to the appearance of horizontal stripes and grooves on the nail cap and other abnormal manifestations. 2. Aging: With ageing, the skin and nails of the hands can be aged, which can make the nail cover become rough, not smooth, and appear horizontal lines and grooves and other manifestations. 3. Nail fungus disease: Nail fungus disease can occur when the nail cover is infected with fungus, which can cause nail malnutrition and loss of luster, and can also cause the nail cover to become rough, loose and thickened, and can appear to be sunken. Nail cover with horizontal grooves should be timely medical treatment, under the guidance of specialists should be timely medical treatment, to help the early cure of the disease.