The transverse groove of the nail cover is called the transverse nail groove, which is mostly caused by the temporary blockage of the formation of nail plate protein. There are many reasons for its appearance, mainly including nutritional factors, traumatic factors, disease factors, and so on. 1. Nutritional factors: If there is a lack of zinc, calcium and other trace elements, it is easy to make the nails undernourished, which will cause the nail cover transverse groove. 2. Traumatic factors: If you cut your nails too short when trimming or have localized trauma to the nail area, it may cause transverse nail grooves. 3. Disease factors: Some infectious diseases, such as gray nails, may affect the formation of nail plate protein, thus forming the transverse nail groove. Some systemic diseases, such as hyperthyroidism, may also cause the nail cover to form transverse grooves. In addition, some special populations, such as infants and young children are prone to develop transverse nail grooves due to hand, foot and mouth disease, and pregnant women are prone to pregnancy, resulting in transverse grooves on the nail cover. If you have horizontal grooves on your fingernails, you can go to the hospital for a checkup to determine the cause of the problem, so that you can begin treatment as soon as possible to avoid delaying the condition, which may lead to other physical problems.