Acute fever with rash is seen in many diseases, such as acute rash infectious diseases, connective tissue diseases, allergic diseases and hematologic diseases, but the most common is acute rash infectious diseases. Although all of these diseases have fever and rash, the relationship between fever and rash, the shape of the rash, and the order of rash are different, so it is not difficult to distinguish them if we observe them carefully. We will list the common febrile diseases with rash1. The shape of the rash and the relationship between the fever and the rash are generally not clearly defined in the case of rash associated with allergic fever, connective tissue disease and hematologic fever, but the rash associated with this non-infectious fever is more common in adults, and connective tissue disease is more common in adult women, and the history of fever is mostly long and accompanied by other related symptoms.