Red rashes all over the body may be associated with eczema, red heat rash, drug rash, acute urticaria and psoriasis. 1. Eczema. It may be caused by allergens such as food, immune abnormalities, chronic insomnia or anxiety causing nervous disorders, etc., resulting in a red rash all over the body. 2. Red prickly heat. Generally formed by sweat overflowing deeper in the epidermis and can be itchy. 3. Drug rash. When certain people take, inject or inhale certain drugs, it may cause inflammatory skin and mucous membrane lesions, resulting in a red rash all over the body, e.g. acetaminophen, tetracycline and other drugs may cause such symptoms. 4. Acute urticaria. Generally by inhalants, food and other allergens, cold, heat, friction and other physical factors, bacteria, viruses and other various pathogens infections related to cause a red rash all over the body. 5. Psoriasis. Psoriasis may be related to heredity, mental stress, bacterial and viral infections, causing a red rash all over the body, which may be covered with silvery-white scales. There are many reasons for the red rash all over the body, and you need to clarify the cause under the guidance of your doctor in order to treat it actively.