This European mint family (Lamiaceae) plant now grows in North America and on other continents as well. The leaf and flower are used medicinally. This plant should not be confused with white horehound, which acts differently.

Black horehound has primarily been used in European traditional herbalism to relieve nausea, anxiety, or the combination of these conditions.¹ It was also used as a mild expectorant and to help normalize menstruation.

Phenylpropanoids—flavonoids and compounds found in the volatile oil of black horehound—are believed to be the plant’s major active constituents.^{5 , 6} A recent test tube study found black horehound phenylpropanoids to have both antioxidant properties and a sedating effect on overactive nerve cells.⁷ Although no human studies have been conducted with black horehound, the herb is believed to be useful for treating nausea associated motion sickness due to a possible effect on the central nervous system.⁸

Black horehound is traditionally used as a tea or tincture. Approximately 2 teaspoons of the leaves are added to 1 cup hot water and allowed to steep for 10 to 15 minutes.⁹ One cup is drunk three times per day. If a tincture is preferred, 1 to 2 ml may be taken three times per day. Black horehound is rarely used alone, and is frequently combined with meadowsweet, chamomile, or ginger for relief of nausea.

There are no reports of adverse effects from use of black horehound when taken in the recommended amounts. Black horehound was traditionally used to treat nausea during pregnancy, though no scientific evaluation of the safety or efficacy of this practice has been conducted. Some sources report that black horehound could induce miscarriage when taken in large amounts.¹⁰ Consult with a doctor who is trained in botanical medicine before using horehound during pregnancy.