Risks of Feverfew

Feverfew, the flowering plant also known as bachelor's buttons, wild camomile and Tanacetum parthenium, has a long history of use as a cultivated garden flower, as well as a folk remedy originating in Europe. According to the University of Maryland Medical Center, a study published in the British Journal of Medicine initiated its current popularity as a migraine remedy. It is available as a supplement, and is sold in bulk bins by natural foods retailers, as well as in capsule, tea, and extract form.
In 2007, the Cambridge University Press published a study concluding that no major safety problems result from the use of feverfew. Still, as with the use of any herbal remedy, you should consult your doctor before taking feverfew.

Misidentification

Whether selecting feverfew capsules at a natural foods store, or harvesting the herb fresh from your garden, be careful to ensure you are identifying the correct herb.
According to Christopher Hobbs of the National Headache Foundation, "It is easy to confuse the medicinal variety of feverfew with chrysanthemum or even other varieties of feverfew--though none of these are toxic, so a mistake would not be injurious."
Though misidentifying the herb may not result in any deleterious effects, taking the wrong supplement would not serve to address your symptoms and would be a waste of time and money.

Anticoagulant

Feverfew may increase bleeding and should not be used by anyone with blood coagulation disorders. According to the Memorial Sloan-Kettering Cancer Center, it is theorized that feverfew may increase the effect of blood thinning medications, such as warfarin. If you are taking blood thinners, do not take feverfew without a doctor's supervision.

Mouth Irritant

As a folk remedy for migraines, some people chew the leaves of the feverfew plant, but the University of Maryland Medical Center notes that such a practice can cause "mouth ulcers, loss of taste, and swelling of the lips, tongue, and mouth." Herbalist Patrick LIma recommends eating the leaves in a sandwich or taking capsules instead to avoid this potential problem.

Allergic Reactions

The daisy family, Compositae, otherwise known as Asteraceae, includes ragweed, marigolds, yarrow, chrysanthemums and, of course, feverfew. The University of Maryland Medical Center reports that feverfew allergies are rare, but they do exist. It is advised that anyone who is allergic to other members of the daisy family refrain from taking feverfew.