Palo Azul (Eysenhardtia polystachya), also known as kidneywood or "blue stick," has a long history of use in traditional Mexican and Central American medicine as a herbal remedy, particularly for urinary tract issues and as a diuretic. Its application for edema—an accumulation of fluid in the body's tissues—arises from its perceived diuretic properties, which are believed to increase urine output and thus help reduce fluid retention. Ethnobotanical records indicate that indigenous peoples and traditional healers have used infusions or decoctions of Palo Azul bark or wood for this purpose, often as part of remedies for "swelling" or "dropsy" (historical terms for edema).

However, scientific validation for the use of Palo Azul in treating edema is limited. There are a few preclinical studies demonstrating mild diuretic effects in animal models, but these are preliminary and do not directly measure outcomes related to edema. No high-quality human clinical trials have established its efficacy or safety for edema specifically. Therefore, while traditional use as a diuretic indirectly supports its application for edema, the overall evidence is weak and largely anecdotal. Health authorities and pharmacopoeias do not currently recognize Palo Azul as a standard treatment for edema.