Red rashes on the body are painless and itchy, and need to be treated according to the etiology. If it is allergic purpura, the original disease needs to be actively treated; syphilitic rashes should be treated with penicillin in a timely manner. 1. Allergic purpura: belongs to the allergic reaction capillary and small vasculitis, which can lead to palpable purpura, ecchymosis and other skin damage, usually not accompanied by itching or pain. It can be treated by actively removing the causative factors, such as preventing and treating upper respiratory tract infections, removing infected lesions, adequate rehydration, and applying topical glucocorticoids. 2. Syphilis rash: belonging to the skin and mucous membrane damage of second-stage syphilis, it may cause skin erythema, papule, patchy rash, which may also be manifested as a red rash on the body without pain or itching. You should consult a doctor in time, improve the serological examination, and follow the doctor’s instructions to use benzylpenicillin and other drugs for treatment after a clear diagnosis. The red rash on the body does not hurt and itchy, there may be other reasons, you need to go to the hospital in time to check, follow the doctor’s instructions for treatment, the specific use of drugs need to follow the doctor’s instructions.