Phellodendron bark, known as "Huang Bai" in Traditional Chinese Medicine (TCM), has a long history of use for treating skin conditions, including acne. In TCM, it is considered to have “heat-clearing” and “dampness-drying” properties, making it a common ingredient in herbal formulas targeting inflammatory skin disorders. Classical Chinese medical texts document its use for "sores" and "damp-heat" skin eruptions, which modern practitioners often interpret as acne or related conditions.

Scientifically, there is limited direct evidence supporting its efficacy for acne. Laboratory studies have identified compounds in Phellodendron bark, such as berberine, with antibacterial and anti-inflammatory effects. Some in vitro studies suggest berberine can inhibit the growth of Propionibacterium acnes (now Cutibacterium acnes), a bacterium involved in acne development, and reduce inflammation. However, clinical trials specifically evaluating Phellodendron bark or its extracts for acne in humans are lacking. Most available data are extrapolated from its general antimicrobial and anti-inflammatory properties or from studies on multi-herb formulations in which Phellodendron is just one component.

In summary, the use of Phellodendron bark for acne is primarily justified by tradition, with some preclinical evidence suggesting possible mechanisms but insufficient clinical research to confirm its effectiveness.