Herb library · Herb · Petasites hybridus
Butterbur
A large-leaved shrub whose root extract has been studied for migraine and whose leaf extract for hay fever. The plant naturally contains substances that can damage the liver and lungs, so only products processed to remove them are ever considered.
Serious warning
The butterbur plant contains pyrrolizidine alkaloids (PAs), which can damage the liver and lungs and may cause cancer. NCCIH says only products processed to remove them and labeled or certified PA-free should be considered, and rare liver injury has been reported even with products said to be PA-free.
Traditional use
It grows in Europe and parts of Asia and North America. Its name comes from the old use of its large leaves to wrap butter in warm weather; in some languages its names mean "rain hat." In the Middle Ages the smoke from burning the roots was thought to fight plague. Today it is sold for migraine and hay fever.
Traditional energetics
Galenic (hot or cold, dry or moist)
Hot and dry in the second degree. Culpeper's Complete Herbal (1814), p. 224 (opens in a new tab)
What studies show
- Limited
Migraine: a butterbur root extract may reduce how often migraines come in adults and children. The American Academy of Neurology recommended it in 2012 but stopped in 2015 because of serious safety concerns.
- Limited
Hay fever: studies of a butterbur leaf extract suggest it may help symptoms.
- Insufficient
Other conditions: little research, and no conclusions can be reached.
Be careful of
Cautions
- NotePA-free products seem safe by mouth for up to 16 weeks in studies, including in children and teens. Side effects can include belching, diarrhea, drowsiness, rash and stomach upset.
- NoteProducts that contain PAs may not be safe on the skin either: PAs could be absorbed through cuts or scrapes.
- AllergyIt may cause an allergic reaction in people allergic to related plants such as ragweed, chrysanthemums, marigolds and daisies.
- PregnancyProducts with PAs should not be used during pregnancy or breastfeeding because they may cause birth defects or liver damage. Little is known about PA-free products in pregnancy or breastfeeding.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“the leaves will begin to spring, which being full grown, are very large and broad, being somewhat thin and almost round”
“It were well if gentlewomen would keep this root preserved, to help their poor neighbours. It is fit the rich should help the poor, for the poor cannot help themselves.”
Sources
- Butterbur: Usefulness and Safety (opens in a new tab) · NCCIH · read September 25, 2026
Reviewed September 25, 2026.