Sudden itching all over the body may be caused by urticaria, neurodermatitis, contact dermatitis and other diseases. 1. Urticaria: the cause may be related to allergy, infection, autoimmune abnormalities and other factors. The patient appears to be a windy mass, accompanied by itching, urticaria is mostly acute, may lead to the whole body suddenly itchy and unbearable. 2. Neurodermatitis: the cause may be related to mental factors, chronic friction and other factors. The patient’s skin will appear mossy changes, accompanied by intense itching, which leads to the patient suddenly itchy all over the body. 3. Contact dermatitis: the cause of the disease is mainly due to skin contact with clothing, bathing products and other exogenous substances caused by allergic reactions. Patients will appear erythema, edema, pimples and other symptoms, often conscious of itching, if suffering from contact dermatitis, may appear all over the body itchy situation. If there is a sudden itch all over the body, it is recommended to go to the regular hospital for examination, to clarify the cause of the disease.