Feverfew (also known as featherfew, featherfoil, or bachelor's buttons) is a perennial, upright, herbaceous plant native to central and southern Europe and naturalized in Australia and most parts of North America. Reaching approximately 60 centimeters in height, feverfew has a finely furrowed, multiple-branched, hairy stem and a strong, bitter smell, which is particularly disliked by bees. The yellowish-green, alternate leaves are roughly 11 centimeters long and 5 centimeters wide, the lower ones with deeply incised lobes and the upper ones divided into two or three pairs of toothed segments. Feverfew flowers from midsummer to fall, bearing numerous small, daisylike blossoms with flat, yellow centers surrounded by 10 to 20 white petals. The leaves of the plant are used for health-promoting purposes.
The active constituents in feverfew leaves are believed to be the sesquiterpene lactones, particularly parthenolide. The leaves also contain flavonoids and volatile oils. Feverfew extracts are commonly standardized for constistent parthenolide levels.
The recommended daily dosage for feverfew is 50 to 1,200 mg of leaf powder. There are no known side effects at this dosage. Feverfew has no known toxicity. Skin exposure to fresh feverfew can cause allergic reactions such as contact dermatitis in some individuals. Because feverfew may interfere with the production of prostaglandins involved in blood clotting, people on blood-thinning medications (such as aspirin or warfarin) should only take feverfew under a physician's close supervision.