Paeonia moutan (commonly known as moutan peony or tree peony root bark, "Mudanpi" in traditional Chinese medicine) has been utilized for centuries in East Asian medical systems. Its use for treating fever is primarily rooted in traditional practices. In Chinese medicine, Mudanpi is categorized as a herb that "clears heat" and "cools the blood," which includes reducing feverish conditions. Classical texts such as the Shennong Bencao Jing and other materia medica describe its use for conditions associated with internal heat, fever, and inflammation.

Modern research has identified compounds in Paeonia moutan such as paeonol, paeonoside, and various flavonoids, which exhibit anti-inflammatory and antipyretic (fever-reducing) properties in some laboratory and animal studies. For example, paeonol has shown fever-lowering effects in rodent models of induced fever. However, robust human clinical trials are lacking, and the evidence remains preliminary. Thus, while there is some pharmacological rationale for its use in fever, the primary justification is historical and traditional practice, rather than strong scientific validation.

In summary, the use of Paeonia moutan for fever is well-established in traditional medicine with some supportive preclinical evidence, but high-quality clinical studies in humans are not available to firmly validate its efficacy or safety for this indication.