Feverfew, adverse effects migraine

In a survey of 270 migraine patients who had been self-treating their headaches by chewing several feverfew leaves daily for 2 to 4 years, 18% of respondents reported adverse effects. The most frequent complaint was canker sores reported by 11.3% of respondents, although only 7% discontinued therapy. Other complaints included sore tongue, abdominal pain, indigestion, tingling sensation, urinary problems, and headaches (Johnson 1983). Canker sores are believed to be a systemic effect that resolves... 

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