This has been shown in a recent study published in the International Journal of Clinical Pharmacology and Therapeutics to be effective in reducing the frequency and severity of attacks of migraine.

A smaller study published in the BMJ in 2002 also suggested that a butterbur extract was as effective in hayfever as one of the mainline drugs but had no sedative effect. A close study of the paper and subsequent correspondence in the BMJ leads the editorial board to doubt that the study's conclusions were accurate and therefore to reserve the use of Butterbur-Petasin for migraine. It is important to note that the hay fever research was carried out using a different extract of the petasin plant than is mentioned above for the migraine research. Extracts of petasites plants may contain pyrrolizidine alkaloids which are powerful cancer producing substances. The extracts marketed as Butterbur-Petasin have NO detectable pyrrolizidine alkaloids and this may be reflected in the migraine trials where no side effects were noted as opposed to the hayfever trial where the pyrrolizidine alkaloids content of their preparation is not mentioned and the side effects occurred in 16.4% of patients.