Clinical tests have shown the use of feverfew may reduce of frequency and severity of headaches. It may be more effective than other nonsteroidal antiinflammatories (NSAIDS), like aspirin. It is the combination of ingredients in the feverfew plant that brings such effective relief. It works to inhibit the release of two inflammatory substances, serotonin and prostaglandins, both believed to contribute to the onset of migraines. By inhibiting these amines as well as the production of the chemical histamine, the herb controls inflammation that constricts the blood vessels in the head and prevents blood vessel spasms which may contribute to headaches.