Acute fever is a sudden onset of high body temperature, typically lasting no more than 7-10 days. If the fever persists for longer than 14 days, it is considered chronic. In traditional Chinese medicine, acute fever is referred to as "external damage," and is usually caused by an external pathogen invading the body. This type of fever is typically treated according to the guidelines laid out in classical Chinese medical texts. However, there are also acute fever patterns that originate from internal pathology.