Nails without crescent moon (nail half-moon, half-moon scar) may be physiological reasons, may also be caused by pathological reasons. 1. Physiological causes: mainly include genetic factors, nail half-moon leaning back, too old, the growth rate of nails is relatively slow, too much stress in life, poor rest and other conditions. 2. Pathological causes: lack of vitamins, lack of trace elements, anemia, digestive and absorption dysfunction or hypothyroidism and other diseases may lead to nails without crescent. Nails without crescent, there are other reasons, if the physiological factors should pay attention to a healthy lifestyle, regular work and rest, do not stay up late, eat a healthy diet, more physical exercise, supplemental nutrition. If it is a pathological factor, you should go to a regular hospital for examination and targeted treatment under the guidance of a professional doctor.