Herb & supplement monograph

Black Horehound Drug Interactions, Uses, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Black Horehound interacts with medications. The heart of this page is the interaction list — every drug Black Horehound is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Black Horehound is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Black Horehound Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Black Horehound drug interaction appears low for most people. None of the listed interactions are rated major, and every one rests on lab findings that have not been reported in humans.

Interactions deserving the most attention

The medications that deserve the most attention are dopamine agonists, a group that includes levodopa, bromocriptine, pramipexole, and ropinirole. Lab research suggests some constituents of black horehound may attach to the same dopamine receptors these drugs target, which could in theory add to their effects. Because these medicines are often carefully balanced for conditions like Parkinson's disease, even a possible added effect is worth knowing about, though nothing like this has actually been seen in people.

What the rest of the list means

The couple dozen medications on the list all fall into this single group, and every entry is rated moderate for the same theoretical reason. In other words, the length of the list reflects how many drugs work through dopamine, not separate proven problems, and no interaction has been confirmed in human use.

Check your medications against Black Horehound

Based on HelloPharmacist’s Black Horehound interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Black Horehound

23 medications have a known interaction with Black Horehound, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Black Horehound using our pharmacist-reviewed interaction data.

AI summaries are generated from our Black Horehound interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Black Horehound combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Black Horehound affects

Every type of medication (drug category) Black Horehound is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 1 drug category Black Horehound interacts with

Dopamine Agonists

Theoretically, black horehound might have additive effects when used with dopamine agonists. Some constituents of black horehound bind to dopamine D2 receptors in vitro; however, this has not yet been reported in humans. Some dopamine agonists include bromocriptine (Parlodel), levodopa (Dopar, component of Sinemet), pramipexole (Mirapex), ropinirole (Requip), and others.

Likelihood Possible Evidence D

Monograph

Black Horehound: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Black horehound is a traditional European herb mainly used for nausea, mild anxiety, and digestive upset, but high-quality human studies are lacking, so its effectiveness is largely unproven. It has a strong, unpleasant smell and taste, and its safety has not been well studied, so it should be avoided in pregnancy and breastfeeding and used cautiously by everyone else.

Scientific name: Ballota nigra
Family: Lamiaceae
Part used: Above-ground parts (flowering tops and leaves)
Common forms: Tea (infusion), liquid extract, tincture, capsules

People commonly use it for

Nausea and vomiting
Anxiety and nervous tension
Sleep problems
Mild digestive upset
Coughs and respiratory complaints

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Limited safety data exist, so use cautiously and talk to a pharmacist first.

PregnancyLikely Unsafe

When used orally; black horehound may affect the menstrual cycle. There is insufficient reliable information available about the safety of black horeh...

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Black horehound (Ballota nigra) is a perennial herb in the mint family. It has dark, square stems, toothed leaves, and small white-to-pale-pink flowers. The plant is native to Europe and parts of Asia and often grows along roadsides, hedges, and waste ground.

The plant is sometimes called "stinking" horehound because of its strong, unpleasant odor. Traditionally, the leaves and flowering tops are dried and used to make teas, tinctures, and extracts. It is not the same plant as white horehound (Marrubium vulgare), even though the names are similar.

In traditional European herbal medicine, black horehound has been used most often for nausea and vomiting, as a mild calming herb, and for minor digestive and breathing complaints.

Uses & effectiveness

Black horehound is best known traditionally as a remedy for nausea and vomiting, including motion sickness and the queasiness that can come with nervousness. It has also been used for anxiety, restlessness, and trouble sleeping, and for mild stomach and respiratory complaints such as coughs.

Despite this long history of use, the scientific evidence is weak. There are very few well-designed human studies, and most information comes from traditional use, laboratory research, or animal studies. Because of this, we cannot say with confidence that black horehound works for any of these conditions.

If you are dealing with ongoing nausea, anxiety, or sleep problems, it is important to talk with a healthcare provider rather than relying on an unproven herb.

How it works

Black horehound contains a variety of plant compounds, including diterpenes (such as ballonigrin and related substances), phenylpropanoids (like verbascoside), and flavonoids. Laboratory studies suggest some of these compounds may have antioxidant activity and may interact with receptors in the nervous system.

Researchers have proposed that the herb may have mild calming and anti-nausea effects, possibly by acting on certain brain chemicals or receptors. However, these ideas come mainly from test-tube and animal research, not from solid human studies.

In short, the way black horehound might work in people is not well understood, and the proposed mechanisms should be considered preliminary.

Safety & precautions

There is not much reliable safety information on black horehound, especially for long-term use or higher doses. Because of this, it should be used with caution and ideally under the guidance of a pharmacist or doctor.

Pregnancy: There is not enough information to know whether black horehound is safe during pregnancy, so it should be avoided.

Breastfeeding: Safety during breastfeeding is also unknown, so it is best to avoid it.

People with liver problems, those taking multiple medications, older adults, and children should be especially cautious and check with a healthcare professional before using this herb. Stop use and seek medical advice if you notice any unusual symptoms.

Side effects

Because black horehound has not been studied carefully, its full side effect profile is not known. Its strong, bitter taste and smell may cause nausea or stomach upset in some people, which is somewhat ironic given that it is used to treat nausea.

As with many herbs, allergic reactions are possible, especially in people sensitive to plants in the mint family. Stop using it and get medical help if you develop a rash, swelling, or trouble breathing.

The effects of large doses or long-term use are unknown, so it is safest to avoid taking more than directed.

Dosing

There is no well-established, standardized dose for black horehound. Traditional use has involved teas made from the dried herb and liquid extracts or tinctures, but reliable dosing from quality human studies is not available.

If you choose to use a product, follow the directions on the label and do not exceed the recommended amount. Because product strength and quality can vary, it is a good idea to choose products from reputable manufacturers.

Always check with a pharmacist or doctor before starting black horehound, especially if you take other medicines or have a health condition.

Pregnancy & Breastfeeding

Black Horehound & Pregnancy

Likely Unsafe

When used orally; black horehound may affect the menstrual cycle. There is insufficient reliable information available about the safety of black horehound used topically or rectally during pregnancy.

Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

Black Horehound & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 2 references that drive our Black Horehound monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
Daels-Rakotoarison DA, Seidel V, Gressier B, et al. Neurosedative and antioxidant activities of phenylpropanoids from Ballota nigra. Arzneimittelforschung 2000;50:16-23. PubMed

Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

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.

Pharmacist Counseling Corner

Black Horehound: Common Questions

Does Black Horehound interact with prescription medications?

Yes. We list 23 medications with a known interaction with Black Horehound. Use the checker above to see how Black Horehound interacts with a specific drug.

How are Black Horehound interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Black Horehound with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Black Horehound interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

What is Black Horehound used for?

It is traditionally used for nausea and vomiting, mild anxiety or restlessness, sleep problems, and minor digestive and breathing complaints. However, strong scientific proof for these uses is lacking.

Is Black Horehound the same as white horehound?

No. Black Horehound (Ballota nigra) and white horehound (Marrubium vulgare) are different plants with different traditional uses, even though their names are similar.

Is Black Horehound safe to take?

Its safety has not been well studied, so it should be used cautiously and ideally with advice from a pharmacist or doctor. It should be avoided during pregnancy and breastfeeding.

Why does Black Horehound smell bad?

It contains strong-smelling plant compounds, which is why it is sometimes called "stinking" horehound. This unpleasant odor and taste is one reason it is often combined with other herbs.

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

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