The causes of gray hair include physiological factors, genetic diseases, acquired diseases, nutritional factors and so on. 1. Physiological factors: When the human body grows older, the function of melanocytes will gradually decay, resulting in hair gradually turning gray and white. 2. Genetic diseases: albinism, pemphigus, phenylketonuria, tuberous sclerosis, histidinemia and other diseases are genetic diseases, which may lead to the symptoms of gray hair. 3. Acquired diseases: Acquired diseases such as vitiligo, epilepsy, Parkinson’s disease, tuberculosis, hyperthyroidism and so on, may appear the symptoms of gray hair. 4. Nutritional factors: when the human body lacks zinc, vitamin B12, folic acid, iron, copper, selenium and other vitamins and minerals, may also cause the symptoms of gray hair. The appearance of gray hair caused by discomfort is recommended to go to the hospital in a timely manner, to identify the cause, follow the doctor’s instructions for treatment.