Phellodendron bark, known as "Huang Bai" in Traditional Chinese Medicine (TCM), has a long history of use in East Asian herbal practice. In TCM, it is primarily prescribed for its "heat-clearing" and "dampness-drying" properties, which sometimes includes use in formulas to address symptoms that overlap with colds, such as fever, sore throat, or inflammation. However, its main traditional indications relate more to urinary tract issues, diarrhea, and skin diseases rather than viral infections like the common cold. There is limited direct historical evidence of its use as an antiviral for colds, but it is occasionally included in multi-herb formulations for respiratory or febrile conditions based on its perceived ability to "clear heat toxins."

Scientifically, a few in vitro studies suggest Phellodendron bark extracts have some activity against certain viruses, likely due to alkaloids such as berberine. However, these studies are preliminary, do not focus specifically on cold viruses (rhinoviruses or coronaviruses), and there is no clinical evidence in humans supporting its efficacy for treating or preventing colds. Thus, while some antiviral effects are hypothesized, the evidence is very limited and mostly based on tradition rather than robust scientific validation.