Chinese Goldthread (Coptis chinensis), known as "Huang Lian" in traditional Chinese medicine (TCM), has a long history of use for treating "heat" and "toxicity" conditions, which in TCM theory often correspond to infectious and inflammatory diseases. Conjunctivitis, referred to as "red eye" or "eye wind," is understood in TCM as a manifestation of heat and toxicity affecting the eyes. Goldthread is valued for its strong "heat-clearing" and "detoxifying" properties, and decoctions or topical preparations containing Goldthread have been used in TCM to alleviate symptoms such as redness, swelling, and discharge associated with conjunctivitis.

The main active compound in Goldthread is berberine, which has demonstrated antibacterial and anti-inflammatory properties in laboratory studies. However, while berberine's antimicrobial effects provide some rationale for its traditional use, high-quality clinical trials specifically evaluating Goldthread or berberine for conjunctivitis in humans are lacking. Most evidence for its effectiveness in this context comes from traditional usage, historical Chinese medical texts, and anecdotal reports. Some modern Chinese herbal formulas for eye conditions include Goldthread as a component, but evidence from randomized controlled trials or systematic reviews is insufficient.

In summary, the use of Chinese Goldthread for conjunctivitis is primarily justified by traditional practice, with some weak scientific plausibility based on known effects of berberine, but there is a lack of robust clinical evidence directly supporting its use for this condition.