I’m considering taking the herb feverfew to help prevent my migraines. Is there any good evidence that it works?—S.B., Orland, Maine

Yes. Several studies have found that supplements of feverfew may reduce migraine frequency and symptoms such as pain, nausea, and sensitivity to light and noise. But a recent analysis of feverfew products sold in the U.S. found huge variations in their concentration and labeled dosage recommendations. Also, feverfew in theory can block a key drug-metabolizing enzyme, leading to a potentially dangerous buildup in blood levels of numerous medications, and it may thin the blood, possibly adding to the effects of blood-thinning drugs. So if you take any medications at all, ask your doctor to check for potential interactions before taking feverfew.