Diseases of the central nervous system: neurasthenia, cerebral arteriosclerosis, cerebral edema and brain tumors can lower the central receptor itch threshold and cause itching of the skin. More wonderfully, brain tumors that infiltrate the base of the fourth ventricle can cause intense and persistent itching of the skin near the nostrils of the face, which then progresses to the entire face and neck. Hematologic disorders: True erythrocytosis is mostly associated with generalized itching of the skin, some of which manifests as burning and stinging pains, aggravated in summer, worse after hot baths, and relieved after half an hour; wonderfully, aspirin can alleviate such itching. About 15-20% of patients with iron deficiency anemia have generalized or localized itching, which can be relieved after iron supplementation and correction of anemia. Chronic renal insufficiency: The skin of uremic patients loses its luster, is dry and flaky. As urea is discharged from sweat glands, it condenses into urea cream, which stimulates the skin and can cause uremic dermatitis, while making the patient feel oddly itchy; at the same time, increased parathyroid hormone in the patient’s body is also the cause of itchy skin. Pregnant women with itchy skin: itchy skin all over the body occurs in healthy pregnant women in the middle and late stages of pregnancy due to biliary stasis in the body, which is clinically called intrahepatic cholestasis of pregnancy. In addition, pregnant women often have itchy skin on the abdominal wall in late pregnancy, which is due to stretching of the abdominal wall and stimulation of sensory nerve endings on the abdominal wall, not due to cholestasis. Diabetes mellitus: Patients with absolute or relative reduction of insulin, which leads to disorders of sugar, fat and protein metabolism, so that pyruvate can not be completely oxidized, pyruvate and lactate accumulate in the nerve tissue, polyneuritis occurs, the patient’s skin is prone to dryness, so that patients appear itchy skin or insect crawling and other abnormal sensations. About 7% of diabetic patients have generalized or restricted pruritus. Abnormal thyroid function: Hyper- and hypothyroidism can also cause pruritus. Itchy skin in hyperthyroidism may be caused by increased basal metabolism, excessive sweating, and stress. Generalized pruritus due to hypothyroid mucinous edema is mostly associated with dry flaky skin. Geriatric skin metabolic disorders: the elderly skin atrophy, and lack of sebum moisturizing, skin blood transport disorders, nutritional deprivation, easy to be stimulated by the hot and cold changes in the surrounding environment, induced pruritus, that is, pruritus of the elderly skin. Therefore, pruritus in the elderly is mostly caused by the loss of skin nourishment. It can develop throughout the year. Hormone levels: reduced hormone levels in the elderly, such as sex hormone levels, are also a cause of pruritus. For example, itchy skin in women during menopause.