Paeonia moutan (commonly known as Moutan Cortex or "Mu Dan Pi" in traditional Chinese medicine) has a long history of use in East Asian herbal medicine. Historically, it is used to "cool the blood," remove blood stasis, and stop bleeding, especially for external bleeding such as wounds, nosebleeds, or minor cuts. The traditional rationale, as recorded in classical texts like the Chinese Pharmacopoeia and Ben Cao Gang Mu (Compendium of Materia Medica), is that Mu Dan Pi has both hemostatic and anti-inflammatory properties. It is often applied topically, sometimes in powdered form, for minor external bleeding. The use is typically accompanied by other herbs in complex prescriptions.

Regarding scientific evidence, there are limited pharmacological studies focusing specifically on the hemostatic effects of Paeonia moutan root bark. Some in vitro and animal studies suggest the presence of compounds (such as paeonol) with anti-inflammatory and vasoconstrictive effects, but direct evidence on its efficacy for external bleeding in humans is lacking. As a result, the use for this purpose remains primarily grounded in traditional practice rather than robust clinical evidence.

In summary, Paeonia moutan is traditionally used for external bleeding, but modern scientific validation of its hemostatic effects is minimal.