Houttuynia cordata, commonly known as fish mint or "yu xing cao" in traditional Chinese medicine (TCM), has a long history of use in East Asian herbal medicine. It has been traditionally employed to "clear heat and remove toxins," which in TCM theory is associated with reducing swelling, particularly of the lymph nodes or glands. Houttuynia is often prescribed for conditions involving swollen lymph nodes, sore throat, and infections, especially those affecting the respiratory or lymphatic systems.

Scientific studies on Houttuynia have primarily focused on its antibacterial, antiviral, anti-inflammatory, and immunomodulatory effects. Laboratory and animal studies have suggested it may inhibit certain pathogens and modulate immune responses. However, there is a lack of high-quality clinical trials directly evaluating its efficacy in reducing lymph node swelling or treating lymphadenopathy in humans. The evidence supporting its use for swollen lymph nodes is therefore largely based on traditional practice, not on rigorous scientific validation.

In summary, while Houttuynia is widely used in traditional medicine for swollen lymph nodes or glands, current scientific evidence specifically supporting this use is limited. Most support comes from its traditional application and some preliminary pharmacological research, but robust clinical data are lacking.