MedlinePlus Herbs and Supplements: White horehound (Marrubium vulgare L.)

Since ancient Egypt, white horehound ( Marrubium vulgare L.) has been used as an expectorant (to facilitate removal of mucus from the lungs or throat). Ayurvedic, Native American, and Australian Aboriginal medicines have traditionally used white horehound to treat respiratory (lung) conditions. The U.S. Food and Drug Administration (FDA) banned horehound from cough drops in 1989 due to insufficient evidence supporting its efficacy. However, horehound is currently widely used in Europe, and it can be found in European-made herbal cough remedies sold in the United States (for example, Ricola®).

There is a lack of well-defined clinical evidence to support any therapeutic use of white horehound. The expert German panel, the Commission E, has approved white horehound for lack of appetite, dyspepsia (heartburn), and as a choleretic. There is promising early evidence favoring the use of white horehound as a hypoglycemic agent for diabetes mellitus and as a non-opioid pain reliever.

There is limited evidence on the safety or toxicity in humans. White horehound has been reported to cause hypotension (low blood pressure), hypoglycemia (low blood sugar), and arrhythmias (abnormal heart rhythms) in animal studies

SynonymsReturn to top

Acylated flavonoid, andorn, blanc rubi, bonhomme, bouenriblé, bull's blood, common hoarhound, eye of the star, grand bon-homme, grand-bonhomme, haran haran, herbe aux crocs, herbe vierge, hoarhound, horehound, hound-bane, houndsbane, labdane diterpene marrubiin, Labiatae (family), Lamiaceae (family), lectins, Llwyd y cwn, maltrasté, mapiochin, mariblé marinclin, marrochemin, marroio, marroio-blanco, marromba, marrube, marrube blanc, marrube commun, marrube des champs, marrube officinal, marrube vulgaire, marrubenol, marrubii herba, marrubiin, marrubio, marrubium, Marrubium vulgare , marruboside, maruil, marvel, mastranzo, mont blanc, phenylethanoid glycosides, phenylpropanoid esters, Ricola®, seed of horus, sesquiterpene, soldier's tea, sterol, weisser andorn.

Note: White horehound should not be confused with black horehound ( Ballota nigra ) or water horehound ( Lycopus americanus , also known as bugleweed).

EvidenceReturn to top

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.

Uses based on scientific evidence	Grade^*
Cough Since ancient Egypt, white horehound has been used as an expectorant. Ayurvedic, Native American, and Australian Aboriginal medicines have traditionally used white horehound to treat respiratory (lung) conditions. The U.S. Food and Drug Administration (FDA) banned horehound from cough drops in 1989 due to insufficient evidence supporting its effectiveness. However, horehound is currently widely used in Europe, and it can be found in European-made herbal cough remedies sold in the United States (for example, Ricola®).	C
Diabetes Animal studies and early human studies suggest that white horehound may lower blood sugar levels. White horehound has been used for diabetes in some countries, including Mexico. Further well-designed human trials are needed.	C
Heartburn/poor appetite In Germany, white horehound is approved for the treatment of heartburn and lack of appetite, based on historical use. There is not enough information from scientific studies to evaluate the effectiveness of white horehound for these conditions.	C
High cholesterol Early study shows that white horehound may lower cholesterol and triglyceride blood levels. Further research is needed to confirm these results.	C
Intestinal disorders/antispasmodic White horehound has been used traditionally to treat intestinal disorders. However, there are few well-designed studies in this area, and little information is available about the effectiveness of white horehound for this use.	C
Pain White horehound has traditionally been used for pain and spasms from menstruation or intestinal conditions. There is a lack of reliable human studies on safety or effectiveness for this use.	C

*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;
F: Strong scientific evidence against this use.

Grading rationale

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 healthcare provider.

Antioxidant, asthma, bile secretion, bloating, blood vessel dilation (relaxation), bronchitis, cancer, cathartic, chronic obstructive pulmonary disease (COPD), colic, congestion, constipation, debility, diarrhea, emetic, fever reduction, flatulence, food flavoring, gallbladder complaints, heart rate abnormalities, high blood pressure, indigestion, intestinal parasites, jaundice (yellowing of the skin), laxative, liver disease, lung congestion, morning sickness, pneumonia, rabies, respiratory (lung) spasms, skin conditions, snake poisoning, sore throat, sweat stimulation, tuberculosis, upper respiratory tract infection, warts, water retention, wheezing, whooping cough, wound healing.

DosingReturn to top

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)

Safety and effectiveness of doses has not been proven. Doses that have been used for cough/throat ailments include 10 to 40 drops of extract in water up to three times a day or lozenges dissolved in the mouth as needed. Ricola® drops are recommended by the manufacturer at a maximum of 2 lozenges every 1 to 2 hours as needed.

Doses recommended by the expert German panel, the Commission E, for treating heartburn or stimulating appetite include 4.5 grams daily of cut herb or 2 to 6 tablespoons of fresh plant juice. Other traditional dosing suggestions are 1 to 2 grams of dried herb or infusion three times daily.

Children (younger than 18 years)

There is not enough information to recommend the safe use of white horehound in children.

SafetyReturn to top

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.

In theory, white horehound may cause an allergic reaction in persons with known allergy or hypersensitivity to members of the Lamiaceae family (mint family) or any white horehound components.

Side Effects and Warnings

White horehound is generally considered to be safe when used as a flavoring agent in foods. However, there is limited scientific study of safety, and most available information is from animal (not human) research. Reported side effects include rash at areas of direct contact with white horehound plant juice, abnormal heart rhythms, low blood pressure, and decreased blood sugar (seen in animals with high blood sugar). White horehound may cause vomiting and diarrhea. Caution is warranted in people with heart disease or gastrointestinal disorders. Caution may also advisable in persons with diabetes or hypoglycemia and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare professional, and medication adjustments may be necessary.

Theoretically, white horehound may interfere with the body's response to the hormone aldosterone, which affects the ability of the kidneys to control the body's levels of water and electrolytes. These theoretical effects may cause high blood pressure, high blood sodium, low potassium, leg swelling, and muscle weakness. Individuals who have high or unstable blood pressure, high sodium, or low potassium or who are taking medications that reduce the amount of water in the body (diuretics, or "water pills") should use caution. White horehound may contain estrogen-like chemicals that either have stimulatory or inhibitory effects on estrogen-sensitive parts of the body. It is unclear what effects may occur in hormone-sensitive conditions such as some cancers (breast, ovarian, uterine) and endometriosis or in people using hormone replacement therapy/birth control pills.

Pregnancy and Breastfeeding

White horehound is not recommended during pregnancy or breastfeeding. Animal studies suggest that white horehound may cause miscarriage.

InteractionsReturn to top

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

Because white horehound is thought to be an expectorant in the treatment of cough or congestion, its use with cold medications that have expectorant ingredients may cause added effects. Theoretically, white horehound may reduce the effects of some medications given for vomiting (serotonin receptor antagonist drugs such as granisetron and ondansetron), migraine headache (ergot alkaloids such as bromocriptine, dihydroergotamine, or ergotamine), and antidepressants that possess serotonin activity (selective serotonin reuptake inhibitors (SSRIs) like Prozac®, Paxil®, or Zoloft®). White horehound may interact with the ability of the body to excrete penicillin. The reported ability of white horehound to cause diarrhea may cause an excessive response when combined with stool softeners or laxatives.

Large amounts of white horehound may increase the risk of abnormal heart rhythms and should be avoided by people treated with drugs that affect heart rhythm. Animal studies suggest that the use of white horehound with medications that lower blood pressure may cause a larger than expected drop in blood pressure. White horehound contains glycoside compounds that act on the heart and these theoretically could affect the activity of glycoside medications such as digoxin (Lanoxin®). Theoretically, white horehound may increase the action of the hormone aldosterone on the kidneys and it may interact with some diuretic medications.

Based on animal studies, white horehound may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional. Medication adjustments may be necessary. In theory, white horehound may also interact with medications used to treat thyroid disorders such as iodine, liothyronine (T3, Cytomel®), methimazole (Tapazole®), propylthiouracil (PTU), thyroxine (T4, Levoxyl®, Synthroid®), and Thyrolar® (T4 plus T3).

White horehound may contain estrogen-like chemicals that either have stimulatory or inhibitory effects on estrogen-sensitive parts of the body. It is unclear what effects may occur in people using hormonal therapies such as birth control pills or hormone replacement therapy. Based on early animal study, white horehound may lower cholesterol or triglyceride blood levels and therefore may have additive effects with other drugs with similar actions.

Interactions with Herbs and Dietary Supplements

In theory, white horehound may lower blood pressure and may cause increased urine production. Caution is advised when using herbs or supplements that lower blood pressure or increase urination.

White horehound may contain glycoside chemicals that affect the heart and therefore should be used with caution by people taking other supplements that have glycoside ingredients. Notably, bufalin/Chan Suis is a Chinese herbal formula that has been reported as toxic or fatal when taken with cardiac glycosides.

Because white horehound may cause diarrhea, use caution if combining it with other laxative herbs.

Animal studies suggest that white horehound 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.

Because white horehound may contain estrogen-like chemicals, the effects of other agents believed to have estrogen-like properties may be altered. In theory, white horehound may interact with agents that affect the thyroid, such as bladderwrack. Based on early animal study, white horehound may lower cholesterol or triglyceride blood levels and therefore may have additive effects with other herbs and supplements with similar actions.

White horehound may interact with herbs and supplements taken to treat cough, vomiting, migraine headache, and depression; use cautiously.

Methodology Return to top

This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com): Ethan Basch, MD (Memorial-Sloan-Kettering Cancer Center); Samuel Basch, MD (Mt. Sinai School of Medicine, NY); Anja Bevens, PharmD (Northeastern University); Dawn Costa, BA, BS (Natural Standard Research Collaboration); Mary McGarry, RPh (University of Rhode Island); David Sollars, MAc, HMC (New England School of Acupuncture); Mamta Vora, PharmD (Northeastern University); Paul Hammerness, MD (Harvard Medical School); Michael Smith, MR PharmS, ND (Canadian College of Naturopathic Medicine); Shaina Tanguay-Colucci, BS (Natural Standard Research Collaboration); Catherine Ulbricht, PharmD (Massachusetts General Hospital); Wendy Weissner, BA (Natural Standard Research Collaboration).

Selected references Return to top

This evidence-based monograph was prepared by the Natural Standard Research Collaboration. The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. Talk to your health care provider before taking any prescription or over the counter drugs (including any herbal medicines or supplements) or following any treatment or regimen. Copyright© 2009 Natural Standard (www.naturalstandard.com). All Rights Reserved.


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White horehound (Marrubium vulgare L.)