Feverfew, a daisy-like perennial found around waste sites and roadsides, appears unexceptional. But for the millions of Americans who suffer from migraines, it holds tremendous promise.

For years, scientists have been exploring its headache-fighting capabilities. What they've found is that feverfew can prevent migraines, though it does not seem to stop those already in progress. Indeed, in one double-blind, placebo-controlled study, use of feverfew was associated with a 70% reduction in migraine frequency and severity. However, later studies have not shown as huge an effect. "This highlights the potential variability of contents and effects of different preparations of the same herb," notes Dr. MaryAnn O'Hara in the Archives of Family Medicine.