Yin Chen (Artemisia capillaris) is a traditional Chinese medicinal herb that has been used for centuries, primarily for conditions related to the liver and the urinary system. In the context of Traditional Chinese Medicine (TCM), Yin Chen is most famous for "clearing heat" and promoting urination, which is why it is commonly included in formulas to support the Bladder body system, especially in cases of damp-heat or jaundice. Classic texts such as the "Shang Han Lun" (Treatise on Cold Damage) include Yin Chen as a key ingredient in formulas like Yin Chen Hao Tang, used for urinary difficulties and jaundice.

The rationale in TCM is that Yin Chen's bitter and cooling properties help to resolve dampness and heat that can accumulate in the Bladder, leading to issues like painful urination, edema, or urinary tract discomfort. Though there are some modern pharmacological studies suggesting anti-inflammatory, choleretic (promoting bile flow), and mild diuretic effects of Artemisia capillaris, the majority of its association with Bladder health comes from historical and traditional usage rather than robust clinical trials.

In summary, Yin Chen's use to support the Bladder body system is primarily justified by traditional Chinese medicine practice, with moderate historical evidence but limited direct scientific validation for this specific use.