Petasin is a bioactive compound found in the butterbur plant (Petasites hybridus). Butterbur extracts standardized for petasin and isopetasin have been used traditionally for various ailments, including headaches and allergic rhinitis, which are related to sinus health. Scientific studies, primarily clinical trials, provide some evidence supporting butterbur's effectiveness in reducing symptoms of allergic rhinitis, a common cause of sinus congestion and inflammation.

Multiple randomized, double-blind studies have shown that butterbur extract can improve symptoms of hay fever (allergic rhinitis) comparably to antihistamines, but with fewer sedative effects. For example, a 2002 study published in the British Medical Journal demonstrated that butterbur extract (standardized for petasin content) was as effective as cetirizine in controlling symptoms in patients with seasonal allergic rhinitis. The mechanism is believed to involve petasin and isopetasin inhibiting leukotriene synthesis, thus reducing inflammation and allergic response in nasal passages.

However, while these findings suggest some benefit for sinus-related conditions, especially those with an allergic component, the evidence is not yet robust or extensive for all sinus disorders. Moreover, concerns about potential hepatotoxicity from pyrrolizidine alkaloids in unprocessed butterbur extracts have limited its widespread medical adoption. Only PA-free standardized extracts are considered safe for use.