Drug Levels and Effects:

Summary of Use during Lactation:

Fennel (Foeniculum vulgare) seeds contain the volatileoilcomposed largely of anethole, as well as fenchone, estragole, 1,8-cineole (eucalyptol), and other constituents. Fennel is a purported galactogogue[1][2][3][4][5][6][7][8][9][10][11] and is included in some proprietary mixtures promoted to increase milk supply. No scientifically valid clinical trials support this use, although one old, small study found an increase in milk volume and fat content with fennel therapy. Galactogogues should never replace evaluation and counseling on modifiable factors that affect milk production.[12] Immersing the breast in a warm infusion of fennel seeds and marshmallow root has been suggested as a treatment for breast inflammation,[13] but no scientific data are available that support this use. Anethole is excreted in breastmilk.[14] Fennel is generally well tolerated in adults, and fenneloilis "generally recognized as safe" (GRAS) for use in food by the US Food and Drug Administration. It has been safely and effectively used alone and with other herbs in infants for the treatment of colic,[15][16][17] so the smaller amounts in breastmilk are likely not to be harmful with usual maternal doses. Some sources recommend limiting the duration of treatment to 2 weeks. Excessive maternal use of an herbal tea containing fennel, anise and other herbs appeared to cause toxicity in 2 breastfed newborns that was consistent with toxicity caused by anethole, which is found in fennel and anise. Fennel can cause allergic reactions after oral or topical use affecting the respiratory system or skin, including photosensitivity. Avoid excessive sunlight or ultraviolet light exposure while using this herbal. Fennel should be avoided by mothers if they or their infants are allergic to carrots, celery, or other plants in the Apiaceae family because of possible cross-allergenicity.

Dietary supplements do not require extensive pre-marketing approval from the US Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed informationabout dietary supplementsis available elsewhere on the LactMed Web site.

Drug Levels:

Maternal Levels.

Eighteen lactating women were given 100 mg of trans-anethol in a capsule on 3 test days. Milk samples were collected every 2 hours for 8 hours starting at the time of ingestion. Trans-anethol was detected in milk at all collection times, with the average concentrations of 2 mcg/L at 0 hours, 9.9 mcg/L at 2 hours, 9.2 mcg/L at 4 hours, 7.3 mcg/L at 6 hours and 4.3 mcg/L at 8 hours after the dose. The average peak anenthol concentration in milk was 23.2 mcg/L. Only small amounts of anenthol glucuronide metabolites were present in the milk samples.[14]

Twelve nursing mothers who were19 weeks to 19 months postpartum ingested 100 mg of 1,8 cineole (eucalyptol) in the form of delayed-release capsules (Soledum-Klosterfrau Vertriebs GmbH, Germany) that release the drug in the intestine. Then they pumped 1 to 4 milk samples at the time they perceived the smell of eucalyptus on their breath which had been previously shown to be approximately concurrent. A total of 21 milk samples were obtained. Odor was rated by a panel of 3 to 5 experts as either smelling like eucalyptus or not. Fourteen of the samples had a distinct eucalyptus-like odor. Chemical analysis of the positive odor tests found 1,8-cineole in concentrations from 70 to about 2090 mcg/kg of milk, most in the range of 100 to 500 mcg/kg of milk. Samples with negative odor tests contained concentrations in the range of 0.98 to about 20.23 mcg/kg of milk. In one woman who donated 3 samples, the highest concentration of 71 mcg/kg occurred at 1.5 hours after ingestion, with concentrations of 1 mcg/kg before ingestion and 15 mcg/kg at 9.5 hours after ingestion.[18]

Infant Levels.

Relevant published information was not found as of the revision date.

Effects in Breastfed Infants:

Two breastfed infants, aged 15 and 20 days, were admitted to the hospital for a reported lack of weight gain in the previous 7 to 10 days, caused by "difficult feeding". The parents reported restlessness and vomiting during the past day. One of the mothers also reported feeling drowsy and weak. On examination, the infants were afebrile but had hypotonia, lethargy, emesis, weak cry, poor sucking and weak responses to painful stimuli. Infant laboratory values, electrocardiograms and blood pressures were normal, and septic work-ups were negative. Both mothers had both been drinking more than 2 liters daily of an herbal tea mixture reportedly containing licorice, fennel, anise, and goat's rue to stimulate lactation. After the mothers discontinued breastfeeding and the herbal tea, the infants improved within 24 to 36 hours. Symptoms of the affected mother also resolved rapidly after discontinuing the herbal tea. After 2 days, breastfeeding was reinstituted with no further symptoms in the infants. Both infants were doing well at 6 months of age. The authors attributed the maternal and infant symptoms to anethole, which is found in both fennel and anise; however, the anethole levels were not measured in breastmilk, nor were the teas tested for their content.[19]

Nursing mothers who were participating in an experiment on the excretion of 1,8-cineole (eucalyptol) in breastmilk took a 100 mg capsule of 1,8-cineole orally. Although instructed not to, 12 mothers breastfed their infants during the experiment. Mothers reported that none of their infants refused their milk or breastfed less than usual. Two mothers felt that their infants were more agitated a few hours after breastfeeding. A third mother reported that the infant stopped nursing from time to time and "looked puzzled", but resumed nursing. Upon repeating the experiment 6 weeks later, the infant did not react in an unusual way during breastfeeding.[18]

Possible Effects on Lactation:

A group of 5 nursing mothers were given no herb for 5 days, 15 mL of a 5 % infusion of fennel seeds 3 times daily for 10 days, followed by another 5-day control period from days 15 to 20. Their diet and environment were kept constant during the study period. Milk volume was measured daily and milk fat percentage was measured on days 5, 10, 15 and 20. Milk volume and fat content increased somewhat during the 10-day treatment period and carried over for 3 to 5 days after discontinuation.[20] Because of the lack of randomization, blinding and controls, and small number of participants, no valid conclusion can be made from this study on the galactogogue effects of fennel.

Sixty-six postpartum mothers (22 in each of 3 groups) with no concurrent illnesses were randomly assigned to receive an herbal tea, placebo, or nothing after delivering healthy, full-term infants. Mothers in the herbal tea group received at least 3 cups daily of 200 mL of Still Tea (Humana-Istanbul, Turkey; containing hibiscus 2.6 grams, fennel extract 200 mg, fenneloil20 mg, roobios 200 mg, verbena [vervain] 200 mg, raspberry leaves 200 mg, fenugreek 100 mg, goat's rue 100 mg, and, vitamin C 500 mg per 100 grams, per manufacturer's web site November 2011). A similar-looking apple tea was used as the placebo. All women were followed by the same nurse and pediatrician who were blinded to what treatment the mothers received. Mothers who received the Still Tea produced more breastmilk with an electric breast pump on the third day postpartum than mothers in the other groups. The infants in the Still Tea group had a lower maximum weight loss, and they regained their birth weights sooner than those in the placebo or no treatment arms. No long-term outcome data were collected. Because many of the ingredients in Still Tea are purported galactogogues, including fennel, no single ingredient can be considered solely responsible for the tea's effects, although the authors attributed the action to fenugreek.[21]


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6. Westfall RE. Galactagogue herbs: a qualitative study and review. Can J Midwifery Res Practice. 2003;2:22-7.
7. Sayed NZ, Deo R, Mukundan U. Herbal remedies used by Warlis of Dahanu to induce lactation in nursing mothers. Indian J Tradit Knowl. 2007;6:602-5.
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9. Abascal K, Yarnell E. Botanical galactagogues. Altern Complement Ther. 2008;14:288-94.
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16. Alexandrovich I, Rakovitskaya O, Kolmo E et al. The effect of fennel (Foeniculum vulgare) seedoilemulsion in infantile colic: a randomized, placebo-controlled study. Altern Ther Health Med. 2003;9:58-61. PMID:12868253
17. Savino F, Cresi F, Castagno E, Silvestro L, Oggero R. 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. PMID:16041731
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Substance Identification:

Substance Name:


Scientific Name:

Foeniculum vulgare

Drug Class:

  • Complementary Therapies

  • Galactogogues

  • Phytotherapy

  • Plants, Medicinal

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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