Purple butterbur root (Petasites hybridus) has scientific support for its use in treating allergic rhinitis. Several randomized, double-blind, placebo-controlled trials have shown that butterbur extract can significantly reduce symptoms such as nasal congestion, sneezing, and itchy eyes in people with allergic rhinitis. In particular, a 2002 study published in the British Medical Journal compared butterbur extract to cetirizine, a common antihistamine, and found butterbur to be similarly effective, but without the sedative side effects. The active compounds, petasin and isopetasin, are believed to inhibit leukotriene synthesis, which plays a key role in allergic inflammation.

Systematic reviews and meta-analyses, including those published in journals such as Phytotherapy Research and Current Allergy and Asthma Reports, generally support butterbur’s efficacy for allergic rhinitis, although they note that more high-quality, large-scale studies are needed. Butterbur extracts used for medicinal purposes are typically processed to remove pyrrolizidine alkaloids, which can be toxic to the liver. Thus, standardized, PA-free butterbur products are considered safe for short-term use in most studies.

In summary, there is moderate to strong scientific evidence supporting the use of purple butterbur root for allergic rhinitis, making it one of the better-studied herbal alternatives for this condition.