Fennel Seeds Side Effects
Fennel gives a licorice-type flavor to foods and is also sometimes used in herbal remedies for aiding digestion and minimizing colic symptoms. Check with your doctor before eating large amounts of fennel seeds, however, because it may not be safe for everyone.
Fennel may make your skin more sensitive to the sun, potentially leading to sun poisoning in some cases. It can also cause skin reactions, and young girls who have used fennel may be more likely to develop breasts prematurely, according to Drugs.com. Choose fennel seeds instead of fennel oil because the oil sometimes causes seizures and hallucinations.
How Much Fennel Is Safe?
Fennel may interact with certain medications, preventing them from being metabolized properly. New York University Langone Medical Center recommends taking ciprofloxacin and other fluoroquinolone medications at least two hours before or after fennel or, preferably, avoiding fennel altogether if you're using one of these antibiotics. This is because it isn't clear if allowing time between taking these substances will eliminate the reaction.
The safety of fennel use for young children and people with kidney or liver disease hasn't been clearly determined. Pregnant women should avoid fennel, which may bring on menstruation and cause a miscarriage. Although some nursing mothers use fennel in an effort to increase milk flow, it isn't clear whether this is safe or effective.
My Fennel Allergy
Fennel contains a substance called estragole, which has been linked to tumors in animal studies. This doesn't necessarily mean fennel isn't safe for people, however, because it contains many other substances that may counter the effect, according to an article published in "Evidence Based Complementary and Alternative Medicine" in 2012. More research is needed to determine whether fennel seeds used in the typical herbal remedy doses actually increase cancer risk in people.
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- Drugs.com: Fennel
- New York University Langone Medical Center: Fennel
- Evidence-Based Complementary and Alternative Medicine: Can Estragole in Fennel Seed Decoctions Really Be Considered a Danger for Human Health? A Fennel Safety Update
- U.S. Department of Agriculture. FoodData Central. Fennel, bulb, raw. 2019.
- Badgujar SB, Patel VV, Bandivdekar AH. Foeniculum vulgare Mill: A Review of Its Botany, Phytochemistry, Pharmacology, Contemporary Application, and Toxicology. Biomed Res Int. 2014;2014:842674. doi:10.1155/2014/842674
- Shahat AA, Ibrahim AY, Hendawy SF, et al. Chemical Composition, Antimicrobial and Antioxidant Activities of Essential Oils from Organically Cultivated Fennel Cultivars. Molecules. 2011;16(2):1366-1377. doi:10.3390/molecules16021366
- Swathi V, Rekha R, Abhishek J, Radha G, Pallavi SK, Praveen G. Effect of Chewing Fennel and Cardamom Seeds on Dental Plaque and Salivary pH – A Randomized Controlled Trial. Int J Pharm Sci Res. 2016;7(1):406-412. doi:10.13040/IJPSR.0975-8232.7
- National Institutes of Health. Office of Dietary Supplements. Vitamin C Fact Sheet for Health Professionals. Updated February 27, 2020.
- Di Ciaula A, Portincasa P, Maes N, Albert A. Efficacy of bio-optimized extracts of turmeric and essential fennel oil on the quality of life in patients with irritable bowel syndrome. Ann Gastroenterol. 2018;31(6):685-691. doi:10.20524/aog.2018.0304
- American Academy of Allergy Asthma and Immunology. Can spices cause allergic reactions? 2020.
- Allergy & ENT Specialists of Central Florida. Fennel. Updated 2015.
- Berkeley Wellness. University of California. Fennel: The Flavor of Sweet Anise. 2016.
- Centers for Disease Control and Prevention. Fruit and Vegetable Safety. Updated February 12, 2020.
Based in Massachusetts, Jessica Bruso has been writing since 2008. She holds a master of science degree in food policy and applied nutrition and a bachelor of arts degree in international relations, both from Tufts University.