1, nail malnutrition: when the human body is short of vitamins or trace elements such as zinc, iron and calcium, many symptoms will appear in the nails, such as downward bending growth of nails, vertical or horizontal stripes, uneven nails, separation of nail beds and so on.
2, fungal infection: when the nail is infected by fungi, the nail may bend downward, causing hooked nails.
3. The nail is too long or improperly trimmed: if the nail is left too long, it is easy to be squeezed and collided, resulting in downward bending growth, or because the nail is cut too deep, the growth speed of the new nail is uneven, generally faster in the middle and slower on both sides, resulting in downward bending of the nail shape.
4, suffering from other diseases: patients with cardiovascular diseases, the front end of the nail body is easy to bend down; Patients with emphysema, liver cirrhosis and other diseases may have the phenomenon that the back of the nail bulges upward and the periphery of the nail bends downward.