Itchy all over the body may be due to decreased sebum secretion, or may be allergic dermatitis, or related to certain systemic diseases. 1. Decreased sebum secretion: dry environment, frequent bathing, or skin aging, can make sebum secretion decrease, no timely replenishment of water or do not pay attention to skin moisturizing, the skin becomes dry and flaky due to lack of water, which can be manifested as itchy skin without any rash. 2. Allergic dermatitis: usually associated with contact with certain allergens, resulting in skin metamorphosis, the main clinical manifestation of itchy skin, there may also be a rash, which allergens may be food, drugs, or close contact with the skin of certain chemical substances. 3. Certain systemic diseases: such as diabetes, tumors, renal insufficiency, liver function abnormalities, etc., will affect the level of hormone secretion, or cause the body metabolic toxins can not be discharged in a timely manner, thus causing itchy skin. As the causes of generalized itching are more, it is recommended that patients to regular hospitals, clear causes, and follow the doctor’s instructions for treatment.