Unknown, although no major safety issues have been identified.
According to a Cochrane systematic review of five studies, feverfew is well tolerated and adverse events are generally mild and reversible. Symptoms were most frequently reported by long-term users and were predominantly mouth ulceration and gastrointestinal symptoms. Contact dermatitis, mouth soreness and lip swelling has also been reported when leaves are chewed.
Controlled studies are not available; therefore, interactions are based on evidence of activity and are largely theoretical and speculative.
Theoretically, feverfew may increase bruising and bleeding; however, although feverfew inhibits platelet aggregation in vitro and in vivo, no effects were seen in a clinical study — observe patients taking this combination.
Theoretically, feverfew may increase bruising and bleeding; however, contradictory evidence exists — observe patients taking this combination.
Contraindications and Precautions
Hypersensitivity to plants in theAsteraceae (Compositae) (daisy) family (e.g. chamomile, ragweed).
Contraindicated in pregnancy.
Practice Points / Patient Counselling
• Although early studies were positive and showed a preventative effect for migraine headache, not all studies have been positive, which may be related to variations in preparations and dosing. Further research is required to determine its place in practice for this indication.
• Of the studies that have produced positive results for migraine therapy, feverfew reduced severity of symptoms such as vomiting and visual disturbances, but did not alter the duration of an episode.
• Tincture or solid-dose preparations may be better tolerated than chewing the fresh leaves, which have been associated with mouth ulcers and lip swelling in some individuals.
• Traditionally, feverfew has also been used to treat coughs and colds, fevers, atonic dyspepsia, worm infestation, menstrual disorders, nervous debility, joint pain and headaches.
• Use is contraindicated in pregnancy.
Answers to Patients’ Frequently Asked Questions
What will this herb do for me?
Some evidence suggests that feverfew may reduce the frequency and severity of migraine headaches; however, test results are inconsistent.
When will it start to work?
Of those studies producing positive results, it appears that approximately 4 months’ continual use may be required; however, in practice, some patients experience benefits within the first 4 weeks.
Are there any safety issues?
Feverfew should not be used in pregnancy. It may increase tendency to bruising and bleeding in patients taking warfarin.