Fennel is a flowering plant with a bulb root that can be eaten. Its seeds are used in food and supplements. It has been used to ease the pain of menstrual cramps. Fennel can be taken as a pill, powder, or extract. It can also be used as a cream, gel, or oil.


30 milligrams every 4 to 6 hours

What Research Shows

May Be Effective

Not Enough Data to Assess

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

It is likely safe to take fennel or use fennel oil on the skin for a short time. Not enough studies have been done to say whether it is safe to use for a long period or during pregnancy or breastfeeding.


Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse. People who are allergic to mugwort, birch, or ragweed should talk to their doctor before taking fennel. It may cause a reaction.


REFA Colic

REFA1 Perry R, Hunt K, et al. Nutritional supplements and other complementary medicines for infantile colic: a systematic review. Pediatrics. 2011 Apr;127(4):720-733.

REFA2 Harb T, Matsuyama M, et al. Infant Colic-What works: A Systematic Review of Interventions for Breast-fed Infants. J Pediatr Gastroenterol Nutr. 2016 May;62(5):668-686.

REFA3 Anheyer D, Frawley J, et al. Herbal Medicines for Gastrointestinal Disorders in Children and Adolescents: A Systematic Review. Pediatrics. 2017 Jun;139(6). pii: e20170062. doi: 10.1542/peds.2017-0062. Epub 2017 May 4. Review. PubMed PMID: 28562281.

REFB Constipation

REFB1 Picon PD, Picon RV, et al. Randomized clinical trial of a phytotherapic compound containing Pimpinella anisum, Foeniculum vulgare, Sambucus nigra, and Cassia augustifolia for chronic constipation. BMC Complement Altern Med. 2010 Apr 30;10:17.

REFC DPMA-Induced Amenorrhea

REFC1 Mohebbi-Kian E, Mohammad-Alizadeh-Charandabi S, et al. Efficacy of fennel and combined oral contraceptive on depot medroxyprogesterone acetate-induced amenorrhea: a randomized placebo-controlled trial. Contraception. 2014 Oct;90(4):440-446.

REFD Dysmenorrhea

REFD1 Ghodsi Z, Asltoghiri M. The effect of fennel on pain quality, symptoms, and menstrual duration in primary dysmenorrhea. J Pediatr Adolesc Gynecol. 2014 Oct;27(5):283-286.

REFD2 Pattanittum P, Kuntanone N, et al. Dietary supplements for dysmenorrhea. Cochrane Database of Systematic Reviews. 2016:CD002124.

REFE Irritable Bowel Syndrome

REFE1 Portincasa P, Bonfrate L, et al. Curcumin and Fennel Essential Oil Improve Symptoms and Quality of Life in Patients with Irritable Bowel Syndrome. J Gastrointestin Liver Dis. 2016;25(2):151-157.

REFF Menopause

REFF1 Rahimikian F, Rahimi R, et al. Effect of Foeniculum vulgare Mill. (fennel) on menopausal symptoms in postmenopausal women: a randomized, triple-blind, placebo-controlled trial. Menopause. 2017 Sep;24(9):1017-1021.

REFG Vaginal Atrophy

REFG1 Yaralizadeh M, Abedi P, et al. Effect of Foeniculum vulgare (fennel) vaginal cream on vaginal atrophy in postmenopausal women: A double-blind randomized placebo-controlled trial. Maturitas. 2016 Feb;84:75-80.

Revision Information

  • Reviewer: EBSCO NAT Review Board Eric Hurwitz, DC
  • Review Date: 07/2019
  • Update Date: 05/06/2020