ATLANTA -- People who suffer from migraines have brains that are more sensitive to all sorts of stimuli such as stress, light and certain foods, all of which can trigger an attack.

While there are prescription medicines for migraines, millions of Americans are turning to herbal remedies to cure what ails them. New research, however, shows that those herbal remedies may do more harm than good.

Experts estimate that 30 million people in the U.S. suffer from migraine headaches, which are accompanied by devastating pain and can make ordinary tasks impossible.

"The key to recognizing a migraine is that the patient has a recurrent pattern of headache and the headache has associated features," said Dr. Sarah DeRossett, a headache specialist. "So, some are very debilitating and are accompanied by nausea and vomiting and light sensitivity."

There are medicines that work to prevent migraines from occurring and ones that sufferers take for treatment while having an attack. The new research is raising concern about people who might unknowingly use migraine medicines along with popular herbal remedies, like ginseng, ginkgo balboa, and St. John's Wort.

"I think anyone who is using St. John's Wort needs to bring that to the attention of their physician," DeRossett said.

St. John's Wort, when taken with prescription anti-depressants that are good for preventing migraine headaches, can dangerously magnify the effect of that medication and create a toxic reaction.

Said DeRossett: "And the result of this could be serious, even fatal."

Also there is some concern that some herbs, including gingko and even valerian root, which is used as a sleep aid, will actually cause or worsen migraine headaches.

"The non-prescription preventatives are not going to be as effective as prescription preventatives," DeRossett said, "And you have to worry about the fact that they are not under FDA regulation."

She said there are some supplements that are not only safe but also effective. They are Vitamin B2, or riboflavin, and magnesium.

"About 15 to 20 percent of the American population is deficient in magnesium," DeRossett said. "And patients who have migraines have lower blood levels of magnesium than patients who don't have migraines."

One of the more popular herbal remedies for migraines is called Fever Few. It has been used to treat fevers and headaches. Some experts have expressed concern that if it is taken with some of the newer medicines used to treat a migraine attack, it can cause a serious reaction.

So, those who suffer from migraines are advised to tell their doctors about all of the supplements they take to prevent the possibility of a negative reaction.