Unmeasured corticosteroid burden may mask safety signals in herbal medicine users: A call for dosage adjustment

We discuss the recent findings by Kim et al. regarding the safety of herbal medicine decoction (HMD) for Bell’s palsy using the National Health Insurance Database. While the study reported no significant difference in adverse events between HMD users and non-users, we raise concerns regarding a potential "masking effect" caused by unmeasured disparities in concomitant corticosteroid utilization. Since high-dose corticosteroids—the standard of care—carry inherent hepatic and renal toxicity, a reduced steroid burden in the HMD group could theoretically mask herb-induced toxicity if the overall adverse event rates appear identical. We propose that the authors perform a sensitivity analysis adjusting for cumulative corticosteroid equivalent dose (CED) within the existing dataset to definitively validate the safety profile of HMD independent of Western medication load.