Fennel Seed Tea

Safety

• Fennel contains estragole, which caused liver tumors in rodents at doses far above what tea supplies. An Austrian survey of 42 fennel teas found that for roughly half of them daily use left a smaller safety margin than regulators aim for, although the authors noted that people usually drink fennel tea only for short periods. Treat it as a short-term herb: 1 to 2 cups a day for up to about 2 weeks at a time (European guidance for adults caps use at 2 weeks), not a lifelong daily habit.
• European herbal-medicine guidance does not recommend fennel preparations during pregnancy or breastfeeding, or for children under 4; for ages 4 to 12 it allows only short courses (under a week) for mild symptoms. Fennel tea is a popular folk remedy for infant colic, but the same survey estimated that, at the upper end, infants given the tea daily could be exposed to about three times as much estragole per kilogram as women, so do not give it to babies without asking a pediatrician.
• Fennel has mild estrogen-like activity. Avoid regular medicinal amounts if you have a hormone-sensitive condition (ER-positive breast cancer, endometriosis or fibroids) or take estrogen-based medicines or tamoxifen.
• Fennel belongs to the carrot family. People allergic to celery, carrot, mugwort or related spices (anise, caraway, coriander, dill) can react with itching or swelling, and should not drink it.
• See a clinician for bloating or abdominal pain that lasts more than 2 weeks, or comes with weight loss, vomiting, blood in the stool or pain that wakes you at night. If you add honey, never give it to babies under 12 months.