Fennel (Foeniculum vulgare)
Natural Standard Bottom Line Monograph, Copyright © 2013 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.
While some complementary and alternative techniques have been studied scientifically, high-quality data regarding safety, effectiveness, and mechanism of action are limited or controversial for most therapies. Whenever possible, it is recommended that practitioners be licensed by a recognized professional organization that adheres to clearly published standards. In addition, before starting a new technique or engaging a practitioner, it is recommended that patients speak with their primary healthcare provider(s). Potential benefits, risks (including financial costs), and alternatives should be carefully considered. The below monograph is designed to provide historical background and an overview of clinically-oriented research, and neither advocates for or against the use of a particular therapy.
Adas (Indonesian, Malay), adas pedas (Malay), alpha-pinene, anason dulce (Romanian), aneth doux (French), anethole, Anethum foeniculum, anis (Tagalog), Anthemis cotula (dog fennel), Apiaceae (parsley family), aptechnyj ukrop (Russian), apteegitilliseemne (Estonian), badesopu (Kannada), badishep (Marathi), bitter fennel, carosella, cây thì là (Vietnamese), common fennel, édeskömény (Hungarian), estragole (methyl chavicol), Fenchel (German), fenchone, fenheli parastie (Latvian), fenhelis (Latvian), fenicol, fenikel (Slovak), fenkel, fenkhel (Russian), fenkoli (Finnish), fenkolo (Esperanto), fennel honey syrup, fennel oil, fenneru (Japanese), fennika (Icelandic), fennikel (Danish, Norwegian), fenouil (French), fenoun (Provençal), fenykl (Czech), ferula communis (giant fennel), finocchio (Italian), finokio (Greek), florence fennel, Foeniculi antheroleum, Foeniculum capillaceum, Foeniculum officinale, Foeniculum vulgare, Foeniculum vulgare ssp. piperitum (bitter fennel), Foeniculum vulgare Mill. var. dulce (sweet fennel), Foeniculum vulgare Mill. var. vulgare (bitter fennel fruits), fructus Foeniculi, funcho (Portuguese), garden fennel, guamoori, haras (Tagalos), harilik apteegitill (Estonian), hinojo (Spanish), hoehyang (Korean), hoehyang-pul (Korean), h?i hương (Vietnamese), hui xiang (Mandarin Chinese), jinten manis (Indonesian), kama (Georgian), komorač (Serbian, Croatian), kopër (Albanian), koper włoski (Polish), koromač (Croatian), large cummin, large fennel, limonene, lus an t'saiodh (Gaelic), madhurika (Sanskrit), maduru (Sinhala), marac (Albanian), maratho (Greek), mehul (Basque), mellet karee (Thai), merula obisnuita, mieloi (Basque), miur belar (Basque), molură (Romanian), morach (Bulgarian), moti saunf (Hindi), mouri (Bengali), pačiolis (Lithuanian), pak chi duanha (Thai), pan modhuri (Oriya), paprastasis pankolis (Lithuanian), pedda jilakarra (Telugu), pennel (Korean), perunjiragam (Tamil), phak si (Laotian), phong karee (Thai), phytoestrogen, razianaj (Arabic), razianeh (Farsi), razyana (Azeri), rezene (Bulgarian, Turkish), samit (Armenian), samong-saba (Burmese), saunf (Hindi), shamaar (Arabic), shamar (Arabic), shamari (Swahili), shamraa (Arabic), shatpushpa (Sanskrit), shoap (Marathi), shoumar (Arabic), shumar (Arabic, Hebrew), siu wuih heung (Cantonese), sladki komarček (Slovenian), sladkij ukrop (Russian), sohikirai (Tamil), so-hoehyang (Korean), sombu (Tamil), sonf (Urdu), sopu (Telugu), spice of the angels, sulpha, sweet cumin, sweet fennel, thian-klaep (Thai), tian hi xiang (Mandarin Chinese), tiêu h?i hương (Vietnamese), tihm wuih heung (Cantonese), trans-anethole, uikyo (Japanese), ukrop sladki (Russian), Umbilliferae (parsley family), venkel (Dutch, Estonian), wariari, wild fennel, wuih heung (Cantonese), xiao hui xiang (Mandarian Chinese), yira (Thai).
Fennel (Foeniculum vulgare) is a native plant of the Mediterranean region. The bulbs, leaves, and seeds are commonly eaten. Fennel has a mild licorice flavor and celery-like texture. It is a good source of potassium.
Fennel fruits have been used as a traditional herbal medicine in Europe and China. Fennel tea has been used as a remedy to treat indigestion in infants.
Good human evidence suggests that fennel reduces colic in infants. According to limited human evidence, fennel may also reduce painful menstruation and protect against damage caused by ultraviolet light. Fennel tea alone or in combination with other herbs is popularly used for gastrointestinal disorders and to improve digestion. However, studies evaluating fennel alone for this use in humans are needed.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Limited research suggests that fennel may reduce infantile colic. Additional studies are needed to confirm these promising findings.
ACE inhibitor-associated cough
Preliminary evidence suggests that fennel may help relieve a cough from using certain blood pressure-lowering drugs called ACE inhibitors (ACEI). However, there is insufficient evidence to make a conclusion for or against its use for ACEI-induced cough.
According to preliminary evidence, fennel, when combined with other herbal agents, may decrease pain associated with colitis (inflammation of the colon). More evidence is needed before further conclusions can be drawn.
Evidence evaluating the effects of fennel combined with other herbal agents suggests that it may reduce constipation. Studies evaluating fennel alone are needed before further conclusions may be drawn.
Dysmenorrhea (painful menstruation)
Fennel has been used to treat painful menstruation. Although preliminary research is promising, further research is needed before conclusions can be drawn.
Hair growth (excessive)
Fennel has been studied in women with hirsutism (excessive facial and body hair), due to its estrogenic effects. More research is needed before further conclusions can be drawn.
According to preliminary evidence, sweet fennel combined with other aromatherapy agents may reduce nausea in patients in hospice programs. More evidence is needed before a conclusion can be drawn.
Ultraviolet light skin damage protection
Topical fennel extract improved sun protection factor (SPF) and decreased ultraviolet light-induced skin reddening. More research is needed in this area.
*Key to grades:A: Strong scientific evidence for this use; B: Good scientific evidence for this use; C: Unclear scientific evidence for this use; D: Fair scientific evidence against this use (it may not work); F: Strong scientific evidence against this use (it likely does not work).
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious and should be evaluated by a qualified health care professional.
Abdominal cramps, abortion (when used in combination), AIDS, allergy, antibacterial, antifungal, antioxidant, antispasmodic, arthritis, asthma, atherosclerosis, attention-deficit hyperactivity disorder (ADHD), bad breath, bloating, bone loss (inhibition of bone resorption), bronchitis, bust enhancer, calming, cancer, cancer preventative (in combination with antioxidants), cognition, cough, Crohn's disease, dementia, diabetes, diabetic complications, digestive disorders, dyspepsia (upset stomach), expectorant, feeling of fullness, flavoring, flu, fragrance, galactagogue (stimulates milk production), gas, gastrointestinal disorders, heart attack, immunomodulator, infections, inflammation, insecticide, intestinal cramps, labor and delivery (facilitates birth), libido, loss of appetite, lymphedema, mosquito repellent, mouth sores, multiple sclerosis, obesity, promotion of menstruation, prostate cancer, psoriasis, sedative, sepsis, sore throat, tuberculosis, upper respiratory tract infections, vision enhancement.
The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
Adults (18 years and older)
For general use as a tea, 1-2 grams of crushed or ground fruit or seed may be added to 150 milliliters of boiling water for 5-10 minutes and strained. One cup of tea has been taken by mouth three times daily. As an antioxidant, doses of 205, 700, and 4,600 micrograms of aqueous extract taken by mouth have been suggested.
For angiotensin converting enzyme (ACE) inhibitor-induced cough, 1-1.5 grams of fennel fruit has been taken by mouth up to three times daily.
For painful menstruation, 25 drops of a 2% concentration of fennel fruit has been taken by mouth every four hours for five days. Thirty drops of fennel every six hours for the first three days of menses have also been taken by mouth, as has 46 milligrams of fennel, taken at the onset of pain or bleeding, five times daily for three days.
For stomach discomfort, 0.1-0.6 milliliters of fennel oil, 5-7 grams of fennel seed, 10-20 grams of fennel syrup and honey, or 5-7.5 grams of tincture has been taken by mouth daily. One to three grams of fennel in 150 milliliters of infusion, 1-3 milliliters of fluid extract 1:1 (grams per milliliter), or 5-15 milliliters of fennel tincture 1:5 (grams per milliliter) have been taken 2-3 times daily between meals. Also, 0.2-0.7 grams of dry extract of fennel 3.9-4.9:1 (weight/weight) has been taken 2-3 times daily.
For inflammation of mucous membranes in the upper respiratory tract, 0.1-0.6 milliliters of fennel oil (equivalent to 0.1-0.6 grams of herb), 5-7 grams of fennel seed, 10-20 grams of fennel syrup or honey, or 5-7.5 grams of tincture has been taken by mouth daily. One to three grams of fennel infusion in 150 milliliters of water, 1-3 milliliters of fluid extract (1:1 grams per milliliter), 5-15 milliliters of tincture 1:5 (grams per milliliter), or 0.2-0.7 grams of dry extract 3.9-4.9:1 (weight/weight) has been taken by mouth 2-3 times daily between meals.
For excess hair growth, 1% and 2% fennel cream has been applied to the skin twice daily for 12 weeks.
For ultraviolet protection, 2% and 5% naturally active botanical fennel have been used in an emulsion on the skin.
Children (under 18 years old)
For colic in infants 2-12 weeks old, 0.1% fennel seed oil in a water emulsion and 0.4% polysorbate-80 has been used for one week.
For inflammation of mucous membranes in the upper respiratory tract, 0.5 grams of the oil per kilogram of body weight has been used. For children aged 1-4 years, 3-6 grams of fennel has been used daily; for those aged 4-10 years, 6-10 grams has been used daily.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Avoid in individuals with a known allergy or hypersensitivity to fennel or other members of the Apiaceae family, including anise, carrot, celery, and mugwort, because of the chance of cross-sensitization. Severe laryngeal swelling, bronchial asthma, hives, or allergic shock may occur. Oral allergy syndrome has been reported with the use of fennel in a woman. Allergic reactions affecting the skin such as atopic dermatitis (chronic skin inflammation) and light sensitivity may occur in patients who consume fennel. Fennel has been reported to provoke reactions in children with food allergy.
Side Effects and Warnings
Fennel seed is likely safe when consumed by mouth by nonallergic individuals in amounts typically found in food. Fennel and fennel tea are generally well tolerated. Allergic reactions and gastrointestinal discomfort are the most common adverse effects, but rarely occur. Fennel oil has Generally Recognized as Safe (GRAS) status for food use in the United States.
Side effects may include an effect on activity of the sympathetic nervous system when the essential oils are inhaled, gastrointestinal complaints, increased menstrual flow, methemoglobinemia (a blood disorder) in infants following ingestion, epileptic seizures with the use of fennel oil, bronchial asthma, hay fever, occupational rhinoconjunctivitis, asthma, and premature breast development in females. In an adult female, severe iron deficiency and problematic upper gastrointestinal irritation developed following the ingestion of pan masala that included fennel seed and betel nut.
Fennel may increase the risk of bleeding. Caution is advised in patients with bleeding disorders or those taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.
Fennel may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Use fennel honey syrup cautiously in diabetic patients, as it is a source of carbohydrates.
Fennel may cause low blood pressure. Caution is advised in patients taking drugs, herbs, or supplements that lower blood pressure and in patients with blood pressure disorders.
Fennel may interfere with the way the body processes certain drugs, herbs, or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of these agents may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. Patients using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Use cautiously when taken by mouth in medicinal amounts for prolonged periods of time, as the constituent estragole is a procarcinogen (a substance that causes cancer after it is broken down by metabolic processes).
Use cautiously in patients using diuretics (agents that increase urination), immunosuppressants, or glaucoma agents.
Because fennel contains estrogen-like chemicals, the effects of other drugs, herbs, and supplements believed to have estrogen-like properties may be altered. Use cautiously in patients using hormone therapy or those with hormone-related disorders such as breast cancer or endometriosis, as fennel has been found to have estrogenic activity.
Use cautiously in patients taking ciprofloxacin or other quinolone antibiotics, as fennel may reduce their absorption.
Use cautiously, as fennel has been reported to be contaminated with Salmonella, Enterobacteriaceae, Serratia, Escherichia, and Yersinia enterocolitica. Cases of botulism have been reported following consumption of fennel.
Use cautiously, as accidental ingestion of 70% alcohol has been reported, due to similar packaging of fennel water and alcohol.
Avoid sweet fennel oil used as aromatherapy in seizure patients, according to the German Commission E monographs.
Avoid in individuals with a known allergy or hypersensitivity to fennel or other members of the Apiaceae plant family, including anise, carrot, celery, and mugwort, because of the chance of cross-sensitization. Severe laryngeal swelling, bronchial asthma, hives, or allergic shock may occur. Oral allergy syndrome has been reported with the use of fennel in a woman. Allergic reactions affecting the skin, such as atopic dermatitis (chronic skin inflammation) and light sensitivity, may occur in patients who consume fennel. Fennel has been reported to provoke reactions in children with food allergy.
Avoid fennel during pregnancy, due to a lack of safety and efficacy data.
Avoid during breastfeeding, as an herbal tea containing fennel reportedly caused neurotoxicity in breastfed infants.
Pregnancy and Breastfeeding
Avoid fennel during pregnancy, due to a lack of safety and efficacy data.
Avoid during breastfeeding, as an herbal tea containing fennel reportedly caused neurotoxicity in breastfed infants.
Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.
Interactions with Drugs
Fennel may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
Fennel may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking insulin or drugs for diabetes by mouth should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Fennel may cause low blood pressure. Caution is advised in patients taking drugs that lower blood pressure.
Fennel may interfere with the way the body processes certain drugs using the liver's cytochrome P450 enzyme system. As a result, the levels of these drugs may be changed in the blood, and may cause increased or decreased effects or potentially serious adverse reactions. Patients using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions.
Because fennel contains estrogen-like chemicals, the effects of drugs believed to have estrogen-like properties may be altered.
Use of fennel and ciprofloxacin (Cipro®) may lead to decreased bioavailability of ciprofloxacin. Theoretically, fennel may also interfere similarly with other fluoroquinolone antibiotics.
Although not well studied in humans, pretreatment with fennel essential oil may enhance the skin absorption of various topical agents, such as trazodone.
Fennel may also interact with antibiotics, anticancer agents, antifungals, anti-inflammatory agents, antiobesity agents, antispasmodics, cholinesterase inhibitors, diuretics (drugs that increase urination), drugs that suppress the immune system, gastrointestinal agents, glaucoma agents, iron salts, pain relievers, vasodilators, and vasopressors.
Interactions with Herbs and Dietary Supplements
Fennel may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
Fennel may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
Fennel may cause low blood pressure. Caution is advised in patients taking herbs or supplements that lower blood pressure.
Fennel may interfere with the way the body processes certain herbs or supplements using the liver's cytochrome P450 enzyme system. As a result, the levels of other herbs or supplements may become too high or too low in the blood. It may also alter the effects that other herbs or supplements possibly have on the P450 system.
Because fennel contains estrogen-like chemicals, the effects of herbs and supplements believed to have estrogen-like properties may be altered.
Although not well studied in humans, pretreatment with fennel essential oil may enhance the skin absorption of various topical agents.
Fennel may interact with antibacterials, anticancer agents, antifungals, anti-inflammatory herbs and supplements, antiobesity herbs and supplements, antioxidants, antispasmodics (drugs for muscle spasms), diuretics (agents that increase urination), eggs, gastrointestinal herbs and supplements, glaucoma agents, herbs that affect the immune system, hormonal herbs and supplements, insect repellants, iron, iron-containing foods, pain relievers, peony, probiotics, vasodilators, and vasopressors.
This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.
Alexandrovich I, Rakovitskaya O, Kolmo E, et al. The effect of fennel (Foeniculum vulgare) seed oil emulsion in infantile colic: a randomized, placebo-controlled study. Altern Ther Health Med 2003;9(4):58-61. View Abstract
Asero R. Fennel, cucumber, and melon allergy successfully treated with pollen-specific injection immunotherapy. Ann Allergy Asthma Immunol 2000;84(4):460-462. View Abstract
Cwikla C, Schmidt K, Matthias A, et al. Investigations into the antibacterial activities of phytotherapeutics against Helicobacter pylori and Campylobacter jejuni. Phytother Res 2010;24(5):649-656. View Abstract
De Vincenzi M, Silano M, Maialetti F, et al. Constituents of aromatic plants: II. Estragole. Fitoterapia 2000;71(6):725-729. View Abstract
Dres C, Johnson C, Loda L. Enzymes and erythema reduction. SPC 1999;71(313):33.
Haze S, Sakai K, Gozu Y. Effects of fragrance inhalation on sympathetic activity in normal adults. Jpn J Pharmacol 2002;90(3):247-253. View Abstract
Ilic S, Duric P, Grego E. Salmonella Senftenberg infections and fennel seed tea. Serbia Emerg Infect Dis 2010;16(5):893-895. View Abstract
Javidnia K, Dastgheib L, Mohammadi Samani S, et al. Antihirsutism activity of Fennel (fruits of Foeniculum vulgare) extract. A double-blind placebo controlled study. Phytomedicine 2003;10(6-7):455-8. View Abstract
Miguel MG, Cruz C, Faleiro L, et al. Foeniculum vulgare essential oils: chemical composition, antioxidant and antimicrobial activities. Nat Prod Commun 2010;5(2):319-328. View Abstract
Modaress Nejad V, Asadipour, M. Comparison of the effectiveness of fennel and mefenamic acid on pain intensity in dysmenorrhoea. East Mediterr Health J 2006;12(3-4):423-427. View Abstract
Muhlbauer RC, Lozano A, Reinli A, et al. Various selected vegetables, fruits, mushrooms and red wine residue inhibit bone resorption in rats. J Nutr 2003;133(11):3592-3597. View Abstract
Namavar JB, Tartifizadeh A, Khabnadideh S. Comparison of fennel and mefenamic acid for the treatment of primary dysmenorrhea. Int J Gynaecol Obstet 2003;80(2):153-157. View Abstract
Picon PD, Picon RV, Costa AF, 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;10:17. View Abstract
Saleh M, Hashem F, Grace M. Volatile oil of Egyptian sween fennel (Foeniculum vulgare, var. dulce. Alef.) and its effects on isolated smooth muscles. Pharm Pharmacol Lett 2005;6(1):5-7.
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(12):1391-1396. View Abstract
Copyright © 2013 Natural Standard (www.naturalstandard.com)
The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.
March 22, 2017