Houttuynia cordata, also known as "fish mint" or "chameleon plant," has a long history of use in traditional East Asian medicine, particularly in China, Korea, and Japan. In traditional Chinese medicine (TCM), Houttuynia is commonly used to "clear heat and remove toxins," and it is often prescribed for infections and inflammations, including conjunctivitis (commonly known as "pink eye"). Classical TCM texts and modern TCM formularies list Houttuynia as an ingredient in eye drops, washes, or decoctions aimed at treating red, swollen, and painful eyes attributed to "wind-heat" or toxin invasion.

The purported benefits in conjunctivitis are mainly attributed to Houttuynia's anti-inflammatory and antimicrobial properties, as observed in laboratory studies. However, robust modern clinical trials specifically investigating the efficacy of Houttuynia for conjunctivitis in humans are lacking. Experimental studies have demonstrated some antibacterial and antiviral activity of Houttuynia extracts, which might theoretically benefit conjunctival infections, but this evidence is preliminary and not yet directly translatable to clinical settings.

In summary, the use of Houttuynia for conjunctivitis is primarily rooted in traditional practice, supported by centuries of anecdotal evidence and inclusion in herbal compendia. While laboratory studies suggest potential mechanisms, high-quality clinical validation is still absent, so the evidence rating remains moderate but is not based on modern scientific trials.