Premature graying of hair can be caused by either kidney yin deficiency or kidney yang deficiency. Hair is one of the outward manifestations of the abundance of kidney essence, which is essential for the growth of hair. Both kidney yang and yin are derived from kidney essence, and both kidney yin and kidney yang deficiencies can cause premature graying of hair. Hair is the source of blood, essence and blood have the same origin, and kidney essence is one of the main substances that produce blood. Therefore, dark and thick hair is a sign of sufficient kidney essence, and on the contrary, thinning, whitening or loss of hair is a sign of kidney essence deficiency. If the phenomenon of premature whitening of the beard hair, you should go to the hospital in a timely manner, after a clear diagnosis by the doctor to arrange a scientific treatment program, so as not to delay the condition.