Cynanchum species are used in traditional medicine systems, particularly in East Asia, for a variety of respiratory ailments, including congestion and sinus issues. In Traditional Chinese Medicine (TCM), some Cynanchum species (for example, Cynanchum stauntonii, known as Bai Qian) are included in herbal formulations to "dispel phlegm" and relieve cough and congestion. The traditional rationale is based on the herb's purported expectorant and anti-inflammatory properties, though these effects are generally described in the context of TCM theory rather than Western biomedical mechanisms.

Scientific studies specifically evaluating Cynanchum for sinus congestion are sparse. Some in vitro or animal studies indicate that extracts from certain Cynanchum species may have anti-inflammatory or immune-modulating effects, but these studies are preliminary and not directly focused on sinus or nasal congestion. There are no robust clinical trials confirming efficacy for human sinus congestion.

In summary, while Cynanchum is traditionally used to help with respiratory congestion, including sinus issues, in systems like TCM, scientific validation for this specific use is limited. The evidence rating is therefore moderate for traditional use but weak in terms of rigorous scientific support.