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Dietary supplement

Fennel Ingredients & Drug Interactions

by Pure Herbs

Fennel label
See full label image
Liquid Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 23, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Fennel against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Fennel is a dietary supplement by Pure Herbs with 1 active ingredient. Its ingredients are commonly taken for digestive upset and bloating, infant colic, menstrual cramps.Based on those ingredients, 740 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Fennel Seed Extract. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Fennel by Pure Herbs

Ask about any prescription or over-the-counter medication and we check it for interactions with Fennel by Pure Herbs — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Fennel by Pure Herbs

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

Pure Herbs Fennel is a liquid extract containing a single active ingredient: fennel seed extract. Fennel has a long history as a culinary spice and traditional herbal remedy, and this liquid form concentrates its compounds for supplemental use.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: relieve gas and menstrual discomfort, support digestion.
  • We looked for evidence on: Flatulence, Dyspepsia, Dysmenorrhea, Constipation, Colic, Nausea and vomiting — and 2 related terms.
  • The strongest evidence on file: Fennel is rated "Possibly Effective" for Dysmenorrhea (Natural Medicines).
  • Also on file: Fennel is rated "Insufficient Reliable Evidence To Rate" for Constipation, Dyspepsia, Flatulence, Nausea and vomiting, and more.

Fennel seed extract is rated possibly effective for dysmenorrhea (painful menstrual periods). For the other conditions in our data—bronchitis, anxiety, nocturnal enuresis (bedwetting), and cholera—the evidence isn't strong enough to establish whether fennel works, so we can't say how well it performs for those uses.

The evidence, ingredient by ingredient Fennel

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Fennel is generally well tolerated when you use food amounts. As a concentrated supplement, though, it warrants more caution.

The most common side effects are gastrointestinal discomfort, sun sensitivity, and allergic reactions in sensitive people. Rarely, seizures have been reported.

Some people have had allergic reactions—like sneezing, wheezing, or difficulty breathing—especially with fresh fennel or fennel-containing products; ground fennel seeds carry a lower risk. Fennel has also been linked to bronchial asthma in some reports.

Avoid medicinal or concentrated amounts during pregnancy due to limited safety data and fennel's hormone-like effects. For breastfeeding, food amounts are likely fine, but medicinal doses and fennel essential oil aren't well studied, so talk with your doctor or pharmacist before using them at higher doses while nursing.

Side effects, ingredient by ingredient Fennel

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Fennel.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 741 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, check with us if you're on anticoagulant or antiplatelet drugs (blood thinners), contraceptive drugs, estrogen replacement therapy, tamoxifen, CYP3A4 substrates, or ciprofloxacin. All of these have moderate interactions with fennel seed extract.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

If you take blood thinners, hormonal contraceptives, hormone replacement therapy, tamoxifen, or CYP3A4-metabolized drugs—or if you're on ciprofloxacin—check with us before starting fennel. It's possibly effective for period pain, but the concentrated form comes with more caution than eating fennel as food.

Avoid it in pregnancy and be mindful of allergy risk if you have a history of spice sensitivities.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Dec 13, 2022.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Fennel, straight from the product label.

Brand Pure Herbs
Net contents 4 Fluid Ounce(s); 120 mL
Market status On market
Date entered into DSLD Dec 13, 2022
DSLD ID 279761
Product type Botanical
Supplement form Liquid
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Women (not pregnant or lactating), Girls: (All), Adult Female (18 - 50 Years), Seniors/Mature (>50 Years) - Women ONLY
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Fennel by Pure Herbs, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
2 mL
Maximum serving Sizes:
2 mL
Servings per container
60
IngredientAmount% DV
Fennel Seed Extract2001 mg--

Other ingredients: None

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Directions: For adults, mix 2 mL (abt. 1/2 tsp) of extract in 2 fl. oz (60 mL) water one time daily preferably with a meal.

Shake well before use

Formulation

Helps to relieve gas, menstrual discomfort and supports healthy digestive function.

FDA Disclaimer Statement

This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Precautions

Warning: Not intended for use by pregnant or nursing women. If you have a medical condition or are taking medication, consult your doctor prior to use.

Discontinue use and consult with your doctor if any adverse reactions occur.

Keep out of reach of children

Brand IP Statement(s)

Pure Herbs, Ltd. Natural Herbal Extracts

FDA Statement of Identity

Dietary Supplement

General Statements

"No expense has been spared to provide the finest nature has to offer."

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Fennel by Pure Herbs label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Fennel label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Fennel by Pure Herbs

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size2 mL Dosage formLiquid Servings per container60 Amounts shown are per serving.

Fennel Seed Extract

Interacts with
740 drugs
2001 mg per serving

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some sm...

Fennel Seed Extract monograph & interactions

Other (inactive) ingredients: None. These complete the product’s ingredient list but are not active constituents.

Interaction report

Fennel by Pure Herbs Drug Interactions

Want to check YOUR meds against Fennel?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
740Drugs
740 Moderate

Ingredients driving the most interactions

Fennel Seed Extract 740

Individual Drug Interactions

The ingredients in Fennel interact with 740 drugs. Click any drug to see the details.

1 of the 1 ingredient in Fennel interact with drugs. Each result below shows which ingredient is responsible. Fennel Seed Extract

Each ingredient & the kinds of drugs it affects

For each ingredient in Fennel with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Fennel Seed Extract6 drug types · 740 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, fennel might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.

Animal research suggests that fennel oil has antithrombotic and antiplatelet effects.

Likelihood Possible Evidence D
Ciprofloxacin (Cipro)

Theoretically, fennel might decrease the levels and clinical effects of ciprofloxacin.

Animal research shows that fennel reduces ciprofloxacin bioavailability by nearly 50%, possibly due to the metal cations such as calcium, iron, and magnesium contained in fennel. This study also found that fennel increased tissue distribution and slowed elimination of ciprofloxacin.

Likelihood Probable Evidence D
Contraceptive Drugs

Theoretically, taking large amounts of fennel might decrease the effects of contraceptive drugs due to competition for estrogen receptors.

Some constituents of fennel have estrogenic activity.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, fennel might increase levels of drugs metabolized by CYP3A4.

In vitro research suggests that fennel inhibits CYP3A4 enzyme activity. This effect has not been reported in humans.

Likelihood Possible Evidence D
Estrogens

Theoretically, taking large amounts of fennel might interfere with hormone replacement therapy due to competition for estrogen receptors.

Some constituents of fennel have estrogenic activity.

Likelihood Possible Evidence D
Tamoxifen (Nolvadex)

Theoretically, taking large amounts of fennel might decrease the antiestrogenic effect of tamoxifen.

Some constituents of fennel have estrogenic activity, which may interfere with the antiestrogenic activity of tamoxifen.

Likelihood Possible Evidence D
Fennel Seed Extract full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Fennel, from the product label.

Pure Herbs

See all Pure Herbs products
Name
Pure Herbs, Ltd.
City
Sterling Heights
State
MI
Phone Number
(800) 860-4372
Web Address
www.pureherbs.com
Pharmacist Counseling Corner

Fennel by Pure Herbs: Common Questions

Does Fennel by Pure Herbs interact with any medications?
Yes. Based on its ingredients, Fennel has a known interaction with 740 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Fennel contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Is fennel seed extract safe if I'm pregnant?
No. Avoid medicinal or concentrated amounts during pregnancy. The safety data is limited and fennel has hormone-like effects that may not be safe for your baby. Stick with fennel as a food seasoning if you use it at all, and ask your doctor or pharmacist before taking this supplement.
What's fennel supposed to help with?
Fennel seed extract is possibly effective for dysmenorrhea—painful menstrual periods. For other uses like anxiety, bronchitis, or bedwetting, we don't have strong enough evidence to say whether it works.
Can fennel cause allergic reactions?
Yes, some people are allergic to fennel. Allergic reactions can include sneezing, wheezing, difficulty breathing, and itchy mouth. They're more common with fresh fennel root than with ground fennel seeds. If you have a history of spice allergies, be extra cautious.
What are the most common side effects?
Orally, fennel is well tolerated overall, but some people report gastrointestinal discomfort, sun sensitivity, or allergic reactions. Seizures are rare but have been reported. It's also been linked to bronchial asthma in some cases.
Is it safe while breastfeeding?
Food amounts of fennel are likely fine, but medicinal doses and fennel essential oil aren't well studied in nursing. Talk with your doctor or pharmacist before taking this supplement at higher doses while breastfeeding.
How does fennel interact with blood thinners?
Animal research suggests fennel has blood-thinning effects of its own. If you're already on anticoagulant or antiplatelet drugs like warfarin or aspirin, fennel could raise your bleeding risk. Check with us before combining them.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Fennel label
Go deeper

The Full Monographs Behind Fennel’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Fennel

Interacts with 740 drugs

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some small studies suggest possible benefit for...

Read the full Fennel monograph →
Sources

Sources & How We Checked

Fennel's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 17 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Fennel 17 references
  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. 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.
  4. Gral N, Beani JC, Bonnot D, et al. [Plasma levels of psoralens after celery ingestion]. Ann Dermatol Venereol 1993;120:599-603.
  5. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246:667-70. PubMed
  6. Rosti L, Nardini A, Bettinelli ME, Rosti D. Toxic effects of a herbal tea mixture in two newborns. Acta Paediatrica 1994;83:683. PubMed
  7. Cuzzolin L, Zaffani S, and Benoni G. Safety implications regarding use of phytomedicines. Eur.J Clin Pharmacol. 2006;62:37-42. PubMed
  8. Tognolini, M., Ballabeni, V., Bertoni, S., Bruni, R., Impicciatore, M., and Barocelli, E. Protective effect of Foeniculum vulgare essential oil and anethole in an experimental model of thrombosis. Pharmacol.Res 2007;56(3):254-260. PubMed
  9. Subehan, Usia, T., Iwata, H., Kadota, S., and Tezuka, Y. Mechanism-based inhibition of CYP3A4 and CYP2D6 by Indonesian medicinal plants. J Ethnopharmacol. 5-24-2006;105(3):449-455. PubMed
  10. Tognolini, M., Barocelli, E., Ballabeni, V., Bruni, R., Bianchi, A., Chiavarini, M., and Impicciatore, M. Comparative screening of plant essential oils: phenylpropanoid moiety as basic core for antiplatelet activity. Life Sci. 2-23-2006;78(13):1419-1432. PubMed
  11. Subehan, Zaidi, S. F., Kadota, S., and Tezuka, Y. Inhibition on human liver cytochrome P450 3A4 by constituents of fennel (Foeniculum vulgare): identification and characterization of a mechanism-based inactivator. J Agric.Food Chem. 12-12-2007;55(25):101 PubMed
  12. LEVY, S. B. Bronchial asthma due to ingestion of fennel and fennel seed. Ann.Allergy 1948;6(4):415.
  13. Ottolenghi, A., De Chiara, A., Arrigoni, S., Terracciano, L., and De Amici, M. [Diagnosis of food allergy caused by fruit and vegetables in children with atopic dermatitis]. Pediatr Med Chir 1995;17(6):525-530.
  14. Trabace L, Tucci P, Ciuffreda L, et al. "Natural" relief of pregnancy-related symptoms and neonatal outcomes: above all do no harm. J Ethnopharmacol. 2015;174:396-402. PubMed
  15. Denaxa D, Arkwright PD. Fennel as a cause of immediate hypersensitivity to toothpaste. Ann Allergy Asthma Immunol. 2020;125(1):99-100. PubMed
  16. Lee HW, Ang L, Lee MS, Alimoradi Z, Kim E. Fennel for reducing pain in primary dysmenorrhea: a systematic review and meta-analysis of randomized controlled trials. Nutrients 2020;12(11):3438. PubMed
  17. Mathew T, John SK, Javali M, Vasireddy M, Nadig R, Sarma GRK. Substance use related cluster headache: A case series. Headache 2022;62(7):908-910. PubMed

See these in context on the Fennel monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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