Andrographis paniculata, commonly known as "king of bitters," is traditionally used in Asian herbal medicine to treat infections, including influenza-like illnesses. Its use for influenza is supported by both traditional practices and a growing body of scientific evidence.

Multiple randomized controlled trials and systematic reviews have evaluated Andrographis for upper respiratory tract infections (URTIs), which include influenza. A 2017 Cochrane review and several meta-analyses found that standardized Andrographis extracts (often 60-120 mg/day andrographolide) can significantly reduce symptoms such as cough, sore throat, and fever compared to placebo, with efficacy similar to standard over-the-counter medications. However, many of these studies included mixed URTIs, not exclusively laboratory-confirmed influenza.

The proposed mechanisms involve the anti-inflammatory and immunomodulatory actions of andrographolide, the main active compound. Some in vitro and animal studies indicate antiviral activity against influenza viruses, but robust clinical evidence for direct antiviral effects in humans is limited.

In summary, while Andrographis paniculata has a strong traditional basis and moderate scientific evidence supporting its symptomatic relief for respiratory infections (including influenza), the evidence is not robustly specific to influenza. Most clinical studies focus on general URTIs, though influenza is often included within these parameters. The evidence rating is moderate (3/5), reflecting positive but not definitive support for its use in treating influenza symptoms.