Butterbur (Petasites hybridus) is a native shrub of Europe, North America, and Asia that has been used by the herbalists for centuries. Modern scientific studies have demonstrated that Butterbur supports healthy blood flow to the brain and healthy neurological function. Petasins, the active constituents in Butterbur, have been shown to play a role in minimizing the frequency and severity of neurological discomfort triggered by bright lights and stress that occasionally occurs in healthy individuals. In addition, Butterbur may help to maintain balanced seasonal immune responses. NOW Butterbur is free of harmful levels of Pyrrolizidine Alkaloids (PA's), so it is safe to use regularly.