Sophora flavescens (commonly known as Ku Shen) has a long history of use in Traditional Chinese Medicine (TCM) for the treatment of skin conditions, including carbuncles, which are clusters of boils caused by bacterial infection. In TCM theory, carbuncles are typically associated with "toxic heat" and dampness, and Sophora flavescens is classified as a bitter and cold herb that 'clears heat,' 'dries dampness,' and 'resolves toxins.'

Classical texts and modern TCM formularies frequently list Sophora flavescens as a component in herbal formulas for treating skin infections, abscesses, and carbuncles. Its traditional use is often in combination with other herbs, such as Lonicera japonica (Jin Yin Hua) and Forsythia suspensa (Lian Qiao), to enhance the antimicrobial and anti-inflammatory effects believed to be necessary for resolving carbuncles.

There is some preliminary pharmacological data indicating that Sophora flavescens possesses antibacterial and anti-inflammatory activity, mostly attributed to its alkaloid components such as matrine and oxymatrine. However, robust clinical evidence supporting its efficacy specifically for carbuncles is lacking. Most of the support for its use in carbuncles comes from historical usage and traditional practice rather than from high-quality scientific studies.

In summary, Sophora flavescens is traditionally used in TCM for carbuncles based on its properties in classical theory and some in vitro findings, but modern clinical validation remains limited.