Dyspepsia, flatulence, bloating, loss of appetite, and for colic in infants. It is used for increasing lactation, promoting menstruation, facilitating birth, and increasing libido.
No concerns regarding safety, available studies validate this statement, when used orally in amounts commonly found in foods. Fennel has Generally Recognized as Safe (GRAS) status in the US.17
There is insufficient scientific information available about the safety of fennel when used in medicinal amounts.
Children: Insufficient reliable information available. Preliminary clinical research suggests that a specific multi-ingredient product containing fennel 164 mg, lemon balm 97 mg, and German chamomile 178 mg (Colimil) is safe in infants when used for up to a week.18 However, maternal consumption of an herbal tea containing fennel has been linked to neurotoxicity in breast-feeding infants.19
Lactation: Possibly Unsafe when used orally by breast-feeding mothers. Case reports have linked consumption of an herbal tea containing fennel to neurotoxicity in two breast-feeding infants.19
Colic. A clinical trial shows that breast-fed infants with colic, who are given a specific multi-ingredient product containing fennel 164 mg, lemon balm 97 mg, and German chamomile 178 mg (Colimil) twice daily for a week, have reduced crying times compared to placebo.18
There is insufficient scientific information available about the effectiveness of fennel for other uses.
Mechanism of Action:
Fennel seed is a rich source of beta-carotene and vitamin C.20 It also contains significant amounts of calcium, magnesium, and iron, and lesser amounts of other metal ions. The seed contains a volatile oil.21 The anethole constituent gives fennel its anise-type aroma and flavor.
Fennel side effects have not been systematically evaluated in clinical research. One clinical trial in infants did not find a significant difference in adverse events compared to placebo.18
Overall low allergic potential except for a small subgroup that cannot tolerate celery, fennel, carrot or mugwort. These are all from the same plant family.R1 pp.383
Interactions with Herbs & Supplements:
Interactions with Drugs:
Interaction Rating = Moderate Be cautious with this combination.
Severity = Moderate • Occurrence = Probable • Level of Evidence = D
Concomitant use of fennel and ciprofloxacin might reduce the effectiveness of ciprofloxacin. Preliminary evidence suggests that fennel reduces ciprofloxacin bioavailability by nearly 50%, possibly due to the metal cations such as calcium, iron, and magnesium contained in fennel. Evidence also suggests that fennel increases tissue distribution and slows elimination of ciprofloxacin.21
Interactions with Foods:
Interactions with Lab Tests:
Oral: No typical dosage. However, traditionally a tea prepared from 1-2 grams of the crushed or ground fruit or seed in 150 mL boiling water has been used. The common dose of the tincture compound is 5-7.5 grams per day. Fennel should be used on a short-term basis. For colic in infants, a specific multi-ingredient product containing fennel 164 mg, lemon balm 97 mg, and German chamomile 178 mg (Colimil) twice daily for a week has been used.18
Dr Clare’s Comments:
A very well tolerated herb. Particularly good for wind and bloating. I have not had a patient who had to give up fennel because of side effects. Many people like the taste as it is somewhat sweet. Fennel is native to the Mediterranean, but is now found throughout the world.
Specific References: FENNEL
17. FDA. Center for Food Safety and Applied Nutrition, Office of Premarket Approval, EAFUS: A food additive database. Available at: vm.cfsan.fda.gov/~dms/eafus.html.
18. Savino F, Cresi F, Castagno E, et al. A randomized double-blind placebo-controlled trial of a standardized extract of Matricariae recutita, Foeniculum vulgare and Melissa officinalis (ColiMil) in the treatment of breastfed colicky infants. Phytother Res 2005;19:335-40.
19. Rosti L, Nardini A, Bettinelli ME, Rosti D. Toxic effects of a herbal tea mixture in two newborns. Acta Paediatrica 1994;83:683.
20. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
21. Zhu M, Wong PY, Li RC. Effect of oral administration of fennel (Foeniculum vulgare) on ciprofloxacin absorption and disposition in the rat. J Pharm Pharmacol 1999;51:1391-6.