Red rashes on a 4-year-old child’s body are considered to be related to environmental factors, mosquito bites, skin allergies, and may also be considered to be related to other diseases. 1. prickly heat: often in a warm and humid environment. Wearing too much clothing, sweat can not be discharged in time, in the skin accumulation, resulting in skin inflammation, may appear red heat rash. 2. Mosquito bites: Being constantly in the outside environment, such as parks and jungles, and being bitten by insects such as lice, bedbugs, mosquitoes, fleas, and mites may cause papular urticaria, resulting in a small red rash on the body. 3. Skin allergy: the skin is stimulated by various factors, which may cause allergic reactions, resulting in red spots, pimples, and itchy bumps on the skin. 4. Other diseases: skin rash with fever, also considered related to acute febrile rash disease, such as measles, infantile emergency rash, scarlet fever, may lead to a red rash on the body. A 4-year-old child with a red rash is associated with a variety of factors. It is recommended to go to the pediatrics and dermatology department of the hospital for examination. Doctors will combine the patient’s condition to make a judgment and give targeted treatment.