Gumweed (Grindelia spp.) has a long history of traditional use for supporting the mucus membranes of the respiratory system, particularly in cases of coughs, bronchitis, and asthma. Native American tribes and 19th-century American herbalists used gumweed preparations as expectorants and to soothe inflamed mucous membranes of the throat and lungs. The plant exudes a sticky resin that was traditionally made into teas, tinctures, or topical applications for these purposes.

The rationale for its traditional use stems from gumweed's mucilaginous properties, which were thought to coat and soothe irritated tissues. There is some pharmacological basis for its expectorant and anti-inflammatory effects, as gumweed contains diterpenes and resinous compounds, but robust clinical trials are lacking. Modern herbal references still cite gumweed for respiratory support, especially for symptoms involving thick or sticky mucus. However, the evidence is primarily historical and anecdotal rather than based on scientific studies or rigorous clinical validation.

In summary, gumweed's use to support mucus membranes is rooted in tradition, with some phytochemical justification but little modern research to confirm efficacy. Its evidence rating reflects reliance on historical precedent rather than scientific validation.