Normal human nails are half of the third phalanx, not too wide, not too narrow, flexible, not easily broken, and have some hardness. The edges are parallel to the flesh, light red, lustrous, without spots or dents, and the nail is mainly composed of protein. The nail plate is soft, white, thin, bendable, brittle, and cracked, which is closely related to congenital abnormalities and lack of vitamin A, vitamin B, vitamin C, as well as lack of necessary trace elements such as iron, calcium, zinc, etc., as well as malnutrition and chronic diseases. There is also a long exposure to water in daily life and other appear easy to break, such people have poorer energy, easy fatigue, like sleep, poor resistance to disease, depression, easy to irritability, you can do relevant tests, such as trace element tests to clarify the cause, if necessary, it is best to eat more food containing iron, and must take vitamin C to improve the ability to absorb iron.