Andrographolide, the main active component of Andrographis paniculata, has a long history of use in traditional medicine systems such as Ayurveda and Traditional Chinese Medicine for treating respiratory ailments, including coughs and congestion. In recent years, scientific studies have begun to investigate its efficacy for respiratory tract infections and related symptoms such as lung congestion.

Clinical trials and meta-analyses have shown that standardized extracts of Andrographis paniculata can reduce symptoms of acute upper respiratory tract infections, including cough, sore throat, and general malaise. Some studies specifically report improvement in symptoms associated with mucus production and chest congestion, likely due to the compound's anti-inflammatory and immunomodulatory effects. Andrographolide has been shown to inhibit pro-inflammatory cytokines and mediators, which may help reduce inflammation in the airways and support mucociliary clearance.

While most studies focus on upper respiratory tract symptoms, there is some evidence from animal and in vitro research suggesting that andrographolide may help reduce pulmonary inflammation and support respiratory function. However, direct high-quality evidence specifically targeting "lung congestion" (as opposed to general upper respiratory tract symptoms) in humans is limited. Therefore, the overall evidence is considered moderate.

In summary, there is scientific rationale and some clinical support for the use of andrographolide in managing symptoms that may include lung congestion, but more targeted research is needed to confirm its effectiveness for this specific symptom.