An itchy rash on the body when scratched may be due to urticaria, eczema, itchy rash and other diseases. 1. Urticaria: related to contact with allergic substances and autoimmune disorders, resulting in the appearance of skin tissue permeability changes, the appearance of limited edema, manifested as varying sizes of mass-like elevations, accompanied by obvious itching, may appear after scratching the situation of the aggravation of the wind. 2. Eczema: it is the result of a variety of internal and external factors, can occur in any part of the body, manifested as erythema, papules, papules and other symptoms, usually accompanied by itching, pimples aggravated by scratching, or even secondary infection, the formation of pustules. 3. itchy rash: the etiology is not clear, may be related to hypersensitivity reactions, genetics, allergies, insect bites and other factors, can be manifested as the skin appeared in varying sizes of pimples, scattered or aggregated distribution, itching is intense, after scratching can appear wind ball-like lesions and herpes papules, repeated scratching may lead to mossy changes, hyperpigmentation and other lesions. The itchy rash may also be caused by other factors, it is recommended that the patient seek medical attention in a timely manner, under the guidance of the doctor for relevant examinations, in order to clarify the diagnosis, symptomatic treatment.