Hedyotis diffusa, also known as Oldenlandia diffusa or "Bai Hua She She Cao" in traditional Chinese medicine (TCM), has a long history of use in East Asian herbal medicine. Its traditional applications include clearing heat, detoxifying, and promoting urination, which relates to its use for symptoms of edema (fluid retention or swelling). In TCM, edema is often conceptualized as the accumulation of dampness or water, and herbs that promote diuresis (increased urine output) are commonly prescribed as therapy.

The evidence supporting Hedyotis diffusa for edema primarily comes from historical texts and longstanding clinical practice, rather than modern scientific studies. Some pharmacological studies have indicated that Hedyotis diffusa contains compounds with anti-inflammatory and mild diuretic properties, but robust clinical trials specifically investigating its efficacy for edema in humans are lacking. Thus, while there is a plausible mechanistic basis and some preclinical data, the majority of support for its use comes from tradition rather than rigorous scientific validation.

In summary, Hedyotis diffusa is traditionally used to help with edema in TCM practice, but scientific evidence supporting its effectiveness for this condition is limited and low in quality.