Supplement analysis backed by scientific evidence · PT

← All supplements
Limited evidenceImmunity

Horehound

White horehound is a traditional cough candy and bitter tonic whose two testable claims have both failed when checked: the FDA removed it from the approved OTC expectorant list for lack of evidence, and the one randomized diabetes trial found it lowered blood glucose by 0.64%.

What the science says

  • Works as a cough expectorant Limited evidence

    The US FDA reviewed horehound as an OTC cough expectorant ingredient and concluded it was not generally recognized as effective, removing it from permitted OTC cough products in 1989. No placebo-controlled trial has since shown it loosens mucus or reduces cough. It remains legal as a flavoring and as a dietary supplement, which is why horehound drops still exist.

  • Lowers blood sugar in type 2 diabetes Limited evidence

    In a double-blind randomized trial of 43 poorly controlled type 2 diabetics, 21 days of Marrubium vulgare leaf infusion reduced fasting glucose by 0.64%, cholesterol by 4.16%, and triglycerides by 5.78% — all clinically meaningless. The comparator herb in the same trial (Cecropia obtusifolia) cut glucose 15.25% and triglycerides 42%. This is a rare case of an herb being directly out-performed inside its own trial.

  • Bitter digestive tonic that stimulates appetite and bile flow Limited evidence

    Horehound's marrubiin and intense bitterness plausibly trigger the standard bitter-receptor reflex increase in salivary and gastric secretion, which is the basis of its European traditional-use registration as an appetite stimulant and dyspepsia remedy. That registration is explicitly based on longstanding use, not on trial evidence; no controlled human study has measured gastric secretion or dyspepsia symptoms with horehound.

  • Anti-inflammatory and analgesic effects Limited evidence

    Aqueous horehound extract shows dose-dependent antinociceptive activity in rodent pain models and antioxidant activity in vitro, mediated largely by marrubiin and phenylpropanoids. These are animal and test-tube results with no human pain trial behind them.

Dosage & safety

Studied doseTraditional preparations: 1-2 g dried herb as an infusion up to three times daily, or 2-6 mL of 1:5 tincture daily; European traditional-use products commonly supply 4.5 g of herb per day. Horehound cough drops contain only flavoring-level amounts. The diabetes trial used a standardized leaf infusion for 21 days and did not work at that dose.
SafetyGenerally regarded as safe in food amounts; large doses cause nausea, vomiting, and diarrhoea, and the herb has documented cardiac-arrhythmia and blood-pressure-lowering effects in animals at high doses. Traditionally considered an emmenagogue and abortifacient — avoid in pregnancy. Theoretical additive effects with antihypertensives and antidiabetic drugs, though the human glucose effect proved negligible. Asteraceae/Lamiaceae contact allergy is possible. Not banned in sport. Note the name confusion: black horehound (Ballota nigra) is a different plant with a different (antiemetic) traditional use.

Scientific references

Where to buy

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in Immunity