The whole body suddenly a large red and itchy considerations may be allergic dermatitis, eczema and other causes, you can take general treatment and medication to deal with the method. 1. General treatment: regulate diet, avoid spicy stimulation and allergic food; avoid sedentary, pay attention to personal hygiene; away from hot and humid environment, keep the indoor temperature and humidity suitable; avoid scratching. 2. Medication: (1) Allergic dermatitis: a skin disease caused by contact with allergic antigens. Patchy, itchy red spots and pimples may appear on the body. Hormonal drugs such as hydrocortisone, prednisone and dexamethasone can be used in this case. (2) eczema: eczema caused by lesions, mainly manifested as red patches on the skin, can also be accompanied by itching, can be used externally halomethasone cream, mometasone furoate cream, hydrocortisone cream and other glucocorticosteroid drugs for treatment. The whole body suddenly up a large red and itchy may also be caused by other reasons, it is recommended that patients seek medical attention in a timely manner to clarify the cause of the disease under the guidance of the doctor for standardized treatment and treatment, the use of drugs need to follow the doctor’s instructions, to avoid self-medication.