Pelargonium, particularly Pelargonium sidoides, has been traditionally used in South African herbal medicine for respiratory tract infections. In recent decades, there has been scientific interest in its potential to support the mucus membranes of the respiratory system. Several randomized, placebo-controlled clinical trials and systematic reviews have investigated the efficacy of standardized extracts (often referred to as EPs 7630) of Pelargonium sidoides in treating acute bronchitis, sinusitis, and the common cold in both adults and children.

The evidence suggests that Pelargonium extract may reduce the duration and severity of symptoms related to upper respiratory tract infections, which involve the mucus membranes. Proposed mechanisms include antimicrobial, antiviral, and immunomodulatory effects, as well as enhancement of mucociliary clearance. The German Commission E and European Medicines Agency recognize its use for acute bronchitis based on clinical data. However, most research has focused on Pelargonium sidoides specifically, rather than other unspecified Pelargonium species.

Overall, while the majority of studies are of moderate quality and some methodological concerns exist, there is moderate scientific support for the use of standardized Pelargonium sidoides extracts in supporting the health of mucus membranes, particularly in the respiratory tract. There is less evidence for other species or for non-standardized extracts.