Home Ingredients White Horehound (Marrubium vulgare)

White Horehound (Marrubium vulgare)

Marrubium vulgare L.
Evidence Level
Preliminary
4 Clinical Trials
6 Documented Benefits
1/5 Evidence Score

White horehound is a bitter herb of the mint family whose dried leaves and flowering tops have long been used in teas, syrups and horehound candy. In the EU it is registered as a traditional herbal medicine, based only on long-standing use, as an expectorant for cough and for occasional bloating and temporary loss of appetite. In the US it is allowed as a flavoring, but the FDA lists horehound among cough expectorant ingredients that lack adequate data for over-the-counter drug use. Human research is very thin: one small trial in adults with type 2 diabetes found almost no change in blood sugar, and a children's cough syrup trial tested horehound only together with ivy, sundew, plantain and honey. Most other findings, including stomach-lining protection and pain-signal effects of its main bitter compound, marrubiin, come from rodent and test-tube studies.

Studied Dose Traditional EU dose for adults and teens over 12: tea of 1 to 2 g dried herb in 250 ml boiling water, 3 times daily (3 to 6 g a day), or 225 to 450 mg powdered herb 3 times daily. No effective dose has been confirmed in human trials.
Active Compound Marrubiin, a bitter labdane diterpene lactone (European Pharmacopoeia minimum 0.7% in the dried herb), plus phenylethanoid glycosides such as acteoside (verbascoside), flavonoids, phenolic acids and tannins; prepared from the dried aerial parts (herb).

Benefits

Traditional herbal use as an expectorant for cough

In the EU, white horehound tea and extracts are registered as a traditional herbal medicine used as an expectorant for cough. The registration rests only on long-standing use, not on clinical trials. In the US, the FDA lists horehound among expectorant ingredients without adequate data to show safety and effectiveness for over-the-counter use.

Supported by Trial 1

Cough scores in a children's multi-herb syrup trial

In a small placebo-controlled trial in 56 children aged 5 to 11 with a recent cough, a syrup combining horehound flower extract with ivy, sundew, plantain and eucalyptus honey lowered day and night cough scores more than placebo over 7 days. Because horehound was one of five ingredients, the result cannot be credited to horehound alone. The trial was industry-sponsored.

Supported by Trial 1

Traditional bitter herb for digestive comfort and appetite

Its bitter taste, mainly from marrubiin, is the basis for traditional use before meals for occasional bloating, flatulence and temporary loss of appetite. The EU recognizes this use on the basis of long-standing use only, with the herb taken about half an hour before meals. No controlled human trials of these uses were found.

Supported by Trial 3

Blood sugar and blood lipids in one small human trial

In a 21-day randomized study, 21 adults with poorly controlled type 2 diabetes added a horehound leaf infusion to their usual treatment. Fasting glucose fell by only 0.64%, cholesterol by 4.16% and triglycerides by 5.78%, and the comparison herb did better. There was no placebo group, and the result does not support a blood sugar benefit.

Supported by Trial 2

Stomach lining and gut muscle effects in animal and lab studies

Animal and lab work only. In mice, a horehound leaf extract and marrubiin reduced stomach lining damage from alcohol or indomethacin and raised stomach pH and mucus. In isolated smooth muscle tissue, a hydroalcoholic extract relaxed contractions caused by several chemical messengers. These findings have not been tested in people.

Supported by Trial 3

Pain-signal effects of marrubiin in mouse studies

Animal work only. Marrubiin injected into mice reduced pain responses in several chemical pain tests in a dose-related way, but it did not change heat-pain response and its effect was not blocked by naloxone, which suggests it does not act through opioid pathways. Injected doses in mice do not show an effect from horehound tea in people.

Supported by Trial 4

Mechanism of action

1

Marrubiin, the main bitter compound

Marrubiin is a labdane diterpene that is characteristic of the Marrubium genus and the main source of the herb's bitterness, typically about 0.12 to 1% of the plant. Bitter compounds are thought to prompt digestive and bile secretions, which is the traditional rationale for taking the herb before meals.

2

Stomach-lining defense signals in mice

In mice, the protective effect of the extract and marrubiin on the stomach lining went along with higher stomach pH and more mucus, and was linked to nitric oxide and the lining's own sulfhydryl compounds. Separately, an extract relaxed smooth muscle contractions in isolated tissue, with apparent selectivity for acetylcholine-driven contractions.

3

Antioxidant phenolic compounds

Horehound contains phenylethanoid glycosides such as acteoside, plus flavonoids and phenolic acids. In test-tube work, a water extract slowed copper-driven oxidation of human LDL and increased HDL-driven cholesterol release from cultured macrophages. Whether drinking the tea has these effects in people is unknown.

Clinical trials

1
Horehound-Containing Herbal Syrup for Children's Cough - Pilot RCT
PubMed

Pilot, randomized, double-blind, placebo-controlled, multicenter trial of Sediflù syrup (eucalyptus honey with dry extracts of horehound flowers, sundew, ivy leaf and plantain leaf), 10 ml twice daily for 7 days; sponsored by Cinfa Laboratories (Núñez et al. 2024, Clin Pediatr (Phila))

56 children aged 5 to 11 years with dry or productive cough lasting 3 to 7 days (27 on syrup, 29 on placebo); 60 were recruited.

Daytime cough scores were significantly lower than placebo from day 3 and nighttime scores from day 4 through day 7. No adverse effects were observed in either group. The amount of horehound per dose was not stated, horehound was one of four herbal extracts plus honey, coughs were milder than expected, and baseline scores were slightly higher in the syrup group.

2
Horehound Leaf Infusion in Adults with Type 2 Diabetes - Comparative Trial
PubMed

Randomized, double-blind 21-day study comparing a Marrubium vulgare dry-leaf infusion with a Cecropia obtusifolia infusion, both added to usual treatment; no placebo group (Herrera-Arellano et al. 2004, Phytomedicine)

43 outpatients with poorly controlled type 2 diabetes; 21 received horehound and 22 received Cecropia.

In the horehound group fasting glucose fell by 0.64%, cholesterol by 4.16% and triglycerides by 5.78%. The between-group comparison found significant differences in glucose and cholesterol lowering, and the authors' positive conclusion concerned the Cecropia infusion, not horehound. A later review noted that this result contradicted earlier mouse studies.

3
Leaf Extract and Marrubiin on Stomach Lining Injury (animal study, not a human trial)
PubMed

Mouse study of a methanol leaf extract (25 to 100 mg/kg) and isolated marrubiin (25 mg/kg) in alcohol-induced and indomethacin-induced stomach injury models, with omeprazole or cimetidine as reference drugs (Paula de Oliveira et al. 2011, J Pharm Pharmacol)

Mice; no human participants.

In the indomethacin model, ulcer inhibition was about 50%, 66% and 82% at 25, 50 and 100 mg/kg of extract, versus about 68% for cimetidine. Marrubiin significantly reduced all measured injury parameters in both models. Extract and marrubiin raised stomach pH and mucus, with effects linked to nitric oxide and sulfhydryl compounds. Not tested in people.

4
Marrubiin in Mouse Pain Models (animal study, not a human trial)
PubMed

Mouse study of marrubiin isolated from Marrubium vulgare, given by injection into the abdominal cavity, in writhing, formalin, capsaicin and hot-plate pain tests (De Jesus et al. 2000, Phytomedicine)

Mice; no human participants.

Marrubiin produced dose-related reductions in pain responses, with ID50 values of 2.2 (writhing), 6.6 and 6.3 (formalin first and second phase) and 28.8 micromol/kg (capsaicin). It did not lengthen hot-plate latency, and naloxone did not reverse its effect, so the authors suggest no opioid involvement. Injected doses in mice, not oral use in people.

Side effects and drug interactions

Common Potential side effects

The EU monograph lists no known side effects at traditional doses, but the herb has not been studied for safety in controlled human trials, and tests for reproductive toxicity, genotoxicity and cancer risk have not been performed.
Avoid if allergic to horehound or other mint-family (Lamiaceae) plants. The EU monograph says not to use it with bile duct obstruction, bile duct inflammation, liver disease or bowel obstruction.
People with an active stomach ulcer, gallstones or other bile disorders should talk to a doctor before use.
Not recommended in pregnancy or breastfeeding because safety has not been established; rat studies summarized in a review reported fewer embryo implantations and uterine and placental changes with an extract. Not recommended for children under 12.
Marrubiin is described as potentially toxic to the liver: in rat and human liver enzyme studies it formed a reactive intermediate. The clinical relevance is unknown.
One case report described serious kidney injury in a 17-year-old after long-term use of a three-herb mix that included horehound, wormwood and centaury; the cause could not be pinned on any single herb.

Important Drug interactions

The EU monograph reports no known interactions, but none have been formally studied in people.
In lab tests, a horehound extract increased the activity of the drug-metabolizing enzymes CYP3A4 and CYP1A2 by more than 50%, which could in theory lower levels of drugs cleared by these enzymes; this has not been confirmed in people. Check with a pharmacist if you take prescription medicines.
Marrubiin is processed by CYP2C9, CYP2C19 and CYP3A4 in liver enzyme studies, so drugs that block these enzymes could change how it is handled.
Animal studies report blood-sugar lowering, although the one human trial found almost no change; people on glucose-lowering medicines should monitor their blood sugar if they use horehound regularly.
Liquid extracts and tinctures contain ethanol, which matters for people avoiding alcohol or taking drugs that interact with it.

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Frequently asked questions about White Horehound (Marrubium vulgare)

Does horehound candy or tea help with a cough?

It has a long history of use for this, and the EU accepts it as a traditional herbal medicine as an expectorant for cough based on that history alone. No trial has tested horehound by itself for cough. One children's trial of a syrup that combined horehound with four other ingredients found lower cough scores than placebo, but it cannot show what horehound contributed. In the US, the FDA lists horehound among expectorant ingredients without adequate data for over-the-counter drug use.

How is white horehound tea usually prepared?

The EU monograph describes steeping 1 to 2 g of the dried, cut herb in 250 ml of boiling water, up to 3 times a day, for adults and teens over 12. For digestive use it is taken about half an hour before meals. The tea is very bitter. The monograph advises seeing a doctor if a cough lasts longer than one week or digestive symptoms last longer than two weeks.

Is horehound safe during pregnancy?

It is not recommended. The EU monograph says safety in pregnancy and breastfeeding has not been established, and animal studies summarized in a review reported fewer embryo implantations and changes to the uterus and placenta with an extract.

Who should avoid white horehound?

Children under 12, pregnant or breastfeeding women, people allergic to mint-family plants, and people with liver disease or bile duct problems should avoid it. Those with a stomach ulcer or gallstones, or who take prescription drugs, should ask a doctor or pharmacist first, since lab work suggests it may affect drug-metabolizing enzymes.

What is White Horehound?

White horehound is a bitter herb of the mint family whose dried leaves and flowering tops have long been used in teas, syrups and horehound candy. In the EU it is registered as a traditional herbal medicine, based only on long-standing use, as an expectorant for cough and for occasional bloating and temporary loss of a…

What is White Horehound used for?

White Horehound has several researched uses. In the EU, white horehound tea and extracts are registered as a traditional herbal medicine used as an expectorant for cough. The registration rests only on long-standing use, not on clinical trials.

What is the recommended dosage of White Horehound?

The clinically studied dose is Traditional EU dose for adults and teens over 12: tea of 1 to 2 g dried herb in 250 ml boiling water, 3 times daily (3 to 6 g a day), or 225 to 450 mg powdered herb 3 times daily. No effective dose has been confirmed in human trials. Always follow the product label and check with a healthcare provider for personal advice.

Is White Horehound safe, and does it have side effects?

Side effects and cautions reported for White Horehound include: The EU monograph lists no known side effects at traditional doses, but the herb has not been studied for safety in controlled human trials, and tests for reproductive toxicity, genotoxicity and cancer risk have not been performed. It may also interact with some medications. White Horehound is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does White Horehound interact with any medications?

Possible interactions include: The EU monograph reports no known interactions, but none have been formally studied in people. In lab tests, a horehound extract increased the activity of the drug-metabolizing enzymes CYP3A4 and CYP1A2 by more than 50%, which could in theory lower levels of drugs cleared by thes… If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for White Horehound?

NutraSmarts rates the evidence for White Horehound as Preliminary (1 out of 5). It is backed by 4 clinical trials and 14 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(14 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Community herbal monograph on Marrubium vulgare L., herba. Final. EMA/HMPC/604271/2012. European Medicines Agency. 2013;EMA/HMPC/604271/2012, adopted 9 July 2013..SourceUsed to support: Official EU herbal monograph, not PubMed-indexed. Recognizes white horehound only as a traditional herbal medicine, based exclusively on long-standing use, as an expectorant in cough associated with a cold, for mild digestive complaints such as bloating and flatulence, and for temporary loss of appetite; no well-established use. Gives tea doses of 1 to 2 g in 250 ml boiling water 3 times daily (3 to 6 g a day), other preparation doses, a minimum age of 12, contraindications (Lamiaceae allergy, bile duct obstruction, cholangitis, liver disease, ileus), a pregnancy and lactation warning, no known interactions or side effects, and notes that reproductive toxicity, genotoxicity and carcinogenicity tests have not been performed.
  2. U.S. Food and Drug Administration. 21 CFR 310.545, Drug products containing certain active ingredients offered over-the-counter (OTC) for certain uses. Electronic Code of Federal Regulations (eCFR). 2026;21 CFR 310.545(a)(6)(iii) and (d)(4). Accessed 2026..SourceUsed to support: US federal regulation, not PubMed-indexed. Lists horehound among OTC expectorant drug ingredients for which, based on evidence available, there are inadequate data to establish general recognition of safety and effectiveness; this applies to products subject to that paragraph from February 28, 1990.
  3. U.S. Food and Drug Administration. 21 CFR 182.20, Essential oils, oleoresins (solvent-free), and natural extractives (including distillates). Electronic Code of Federal Regulations (eCFR). 2026;21 CFR 182.20. Accessed 2026..SourceUsed to support: US federal regulation, not PubMed-indexed. Lists horehound (hoarhound), Marrubium vulgare L., among natural extractives generally recognized as safe for their intended use in food, which covers flavoring use rather than any health use.
  4. Núñez C, Chiatti MC, Tansella F, Coronel-Rodríguez C, Risco E. Efficacy and tolerability of SEDIFLÙ in treating dry or productive cough in the pediatric population (SEPEDIA): A pilot, randomized, double-blind, placebo-controlled, multicenter clinical trial. Clin Pediatr (Phila). 2024;63(11):1510-1519. doi: 10.1177/00099228241228074.PubMedUsed to support: Pilot randomized placebo-controlled trial in 56 children aged 5 to 11 with recent cough: a syrup of eucalyptus honey with horehound flower, sundew, ivy leaf and plantain leaf extracts, 10 ml twice daily for 7 days, lowered daytime cough scores versus placebo from day 3 and nighttime scores from day 4, with no adverse effects observed. Horehound dose not stated; effects cannot be attributed to horehound alone; sponsored by Cinfa, with two authors advisors to the company.
  5. Herrera-Arellano A, Aguilar-Santamaría L, García-Hernández B, Nicasio-Torres P, Tortoriello J. Clinical trial of Cecropia obtusifolia and Marrubium vulgare leaf extracts on blood glucose and serum lipids in type 2 diabetics. Phytomedicine. 2004;11(7-8):561-6. doi: 10.1016/j.phymed.2004.01.006.PubMedUsed to support: Randomized double-blind 21-day study in 43 adults with poorly controlled type 2 diabetes comparing two herbal infusions added to usual care, without a placebo arm. In the 21 people given horehound leaf infusion, fasting glucose fell 0.64%, cholesterol 4.16% and triglycerides 5.78%; the authors' positive conclusion concerned the other herb, Cecropia obtusifolia.
  6. Rodríguez Villanueva J, Martín Esteban J, Rodríguez Villanueva L. A Reassessment of the Marrubium Vulgare L. Herb's Potential Role in Diabetes Mellitus Type 2: First Results Guide the Investigation toward New Horizons. Medicines (Basel). 2017;4(3):57. doi: 10.3390/medicines4030057.PubMedUsed to support: Review noting that only one clinical trial of horehound has been run, for blood sugar in type 2 diabetes, that its results contradicted earlier mouse studies, and that the trial's methods should be reevaluated.
  7. Aćimović M, Jeremić K, Salaj N, Gavarić N, Kiprovski B, Sikora V, Zeremski T. Marrubium vulgare L.: A Phytochemical and Pharmacological Overview. Molecules (Basel). 2020;25(12):2898. doi: 10.3390/molecules25122898.PubMedUsed to support: Review of horehound chemistry and pharmacology: marrubiin is the characteristic, predominant bitter labdane diterpene (about 0.12 to 1% of the plant; minimum 0.7% in the dried herb), with phenylethanoid glycosides such as acteoside, flavonoids, phenolic acids and tannins. Describes traditional cough, expectorant and bitter-tonic use, notes that animal pregnancy studies reported fewer implantations and uterine and placental changes, and concludes that well-designed clinical trials are still needed. It gives the diabetes trial as 22 patients, while the trial abstract reports 21 in the horehound group.
  8. Paula de Oliveira A, Santin JR, Lemos M, Klein Júnior LC, Couto AG, Meyre da Silva Bittencourt C, Filho VC, Faloni de Andrade S. Gastroprotective activity of methanol extract and marrubiin obtained from leaves of Marrubium vulgare L. (Lamiaceae). J Pharm Pharmacol. 2011;63(9):1230-7. doi: 10.1111/j.2042-7158.2011.01321.x.PubMedUsed to support: Mouse study, not human evidence: a methanol leaf extract (25 to 100 mg/kg) and marrubiin (25 mg/kg) reduced alcohol- and indomethacin-induced stomach injury, raised stomach pH and mucus, and the protection was linked to nitric oxide and sulfhydryl compounds.
  9. De Jesus RA, Cechinel-Filho V, Oliveira AE, Schlemper V. Analysis of the antinociceptive properties of marrubiin isolated from Marrubium vulgare. Phytomedicine. 2000;7(2):111-5. doi: 10.1016/S0944-7113(00)80082-3.PubMedUsed to support: Mouse study, not human evidence: injected marrubiin reduced pain responses in writhing, formalin and capsaicin tests in a dose-related way, did not change hot-plate latency, and was not reversed by naloxone, suggesting no opioid involvement.
  10. Schlemper V, Ribas A, Nicolau M, Cechinel Filho V. Antispasmodic effects of hydroalcoholic extract of Marrubium vulgare on isolated tissues. Phytomedicine. 1996;3(2):211-6. doi: 10.1016/S0944-7113(96)80038-9.PubMedUsed to support: Lab study on isolated smooth muscle tissue, not human evidence: a hydroalcoholic extract of horehound inhibited contractions caused by acetylcholine, bradykinin, prostaglandin E2, histamine and oxytocin, with apparent selectivity for cholinergic contractions.
  11. Berrougui H, Isabelle M, Cherki M, Khalil A. Marrubium vulgare extract inhibits human-LDL oxidation and enhances HDL-mediated cholesterol efflux in THP-1 macrophage. Life Sci. 2006;80(2):105-12. doi: 10.1016/j.lfs.2006.08.040.PubMedUsed to support: Test-tube study, not human evidence: a water extract of horehound (up to 100 micrograms/ml) prolonged the lag phase of copper-induced human LDL oxidation, slowed lipid peroxidation, and increased HDL-mediated cholesterol efflux from THP-1 macrophages.
  12. Haron MH, Dale O, Martin K, Avula B, Chittiboyina AG, Khan IA, Gurley BJ, Khan SI. Evaluation of the Herb-Drug Interaction Potential of Commonly Used Botanicals on the US Market with Regard to PXR- and AhR-Mediated Influences on CYP3A4 and CYP1A2. J Diet Suppl. 2023;20(5):763-776. doi: 10.1080/19390211.2022.2110351.PubMedUsed to support: Lab screen of 30 popular US botanical extracts: horehound was one of eight that induced both CYP3A4 and CYP1A2 activity by more than 50%. The authors note that in vivo studies are needed to judge clinical relevance.
  13. Xing Y, Xing H, Ma Y, Liu Q, Xu S. In Vitro and In Vivo Studies of Metabolic Activation of Marrubiin, a Bioactive Constituent from Marrubium Vulgare. Chem Res Toxicol. 2021;34(9):2157-2165. doi: 10.1021/acs.chemrestox.1c00250.PubMedUsed to support: Rat and human liver enzyme study plus rat bile analysis: marrubiin, described as having potential liver toxicity, is converted into a reactive intermediate that binds glutathione, mainly by CYP2C9, CYP2C19 and CYP3A4. Shows a possible toxicity pathway, not harm in people.
  14. Selles A, Afir Y, Rahou Y, Debchi L, Rafa-Debbah H, Bahriz MR, Benziane A. Acute Kidney Injury Following the Ingestion of a Medicinal Plants' Mixture: A Case Report. Case Rep Nephrol. 2024;2024:8207758. doi: 10.1155/crin/8207758.PubMedUsed to support: Single case report: a 17-year-old developed severe acute kidney injury with interstitial nephritis on biopsy, attributed to chronic intake of a mixture of Artemisia absinthium, Marrubium vulgare and Centaurium erythraea. A single case with three herbs cannot show which herb, if any, was responsible.