Horizontal lines on the nail cover can be caused by nail malnutrition, local irritation, nail fungus disease, skin disease with nail damage and other factors. 1. Nail malnutrition, local stimulation: Nail malnutrition may be related to local trauma to the nails, lack of micronutrients due to partial diet, excessive use of detergents and disinfectants, long-term manicure and other factors, which can lead to poor growth and development of the nail cover, and the appearance of horizontal stripes. 2. Nail fungal disease: after the nails are infected by fungi and other pathogens, local fungal infections may occur, which may lead to changes in the appearance, color and shape of the nails, and the manifestation of horizontal stripes may appear. 3. Skin diseases with nail damage: chronic inflammatory skin diseases such as lichen planus and psoriasis can be accompanied by symptoms of bleeding nail damage, which can be manifested as horizontal lines on the nail cover. When you find horizontal lines on the nail cover, you should consult a doctor in time, and under the guidance of a specialist, you can actively carry out appropriate treatment, which will help to alleviate the uncomfortable symptoms as soon as possible.