Educational information, not medical advice — ask your doctor or midwife.
Kanzoto is a Kampo medicine made from one herb only: licorice root (Glycyrrhiza). It is used short-term for a sudden sore throat and for a dry, tickly cough with little or no phlegm.
The name means "licorice decoction". It is a single drug (Kampo) formula, which is unusual, since most Kampo medicines combine several herbs. Traditionally it is sipped slowly or held in the mouth so the sweet liquid coats the throat.
Honest verdict on the evidence: Kanzoto has a long and respected place in Kampo practice, but we could not identify published human trials testing this formula for sore throat or cough. Long traditional use tells you a preparation has been trusted for a long time; it is not the same as proof that it works, and this is the only place in this document we will say so.
One more thing to know before you read on. Licorice is not a bland herb. Taken in large amounts or for more than a short course it can push down your potassium, raise your blood pressure and affect your heart rhythm, so Kanzoto is meant for a few days of use, not as a daily tonic.
Kanzoto is thought to soothe and coat an irritated throat, which may calm the urge to cough. This is the traditional explanation and it has not been confirmed in people.
Laboratory work shows that licorice constituents can reduce inflammation (swelling and irritation) and that they have some antiviral and mucus-soothing activity in cell and animal studies. Whether any of that happens at the dose you would actually swallow is unknown.
Glycyrrhizin, the main sweet compound in licorice, also blocks an enzyme in the kidney that normally protects the body from cortisol. That is the same action behind its side effects, so the helpful and the harmful effects come from one source.
Kanzoto usually comes in one of three forms. The choice is mostly about convenience.
Dried decoction: cut licorice root simmered in water and sipped warm, which is the classical method. Granules or fine powder: a dried extract sold in sachets in Japan and mixed into hot water. Tablets or capsules: less traditional, and they skip the throat-coating step that the liquid gives.
Strength varies a lot between brands, so the amount of licorice in one sachet is not a fixed number. Check the label for the raw-herb equivalent or the glycyrrhizin content before you decide on a dose.
Kanzoto is old. It appears as Gancao Tang in the Shanghan Lun, a Chinese medical text from roughly the third century, and it was carried into Japanese Kampo practice, where it is still a listed formula today.
Its classical indication was a painful throat, and later Kampo writers extended it to sudden dry coughing fits. Because it is a single herb, it was often the first thing tried before moving to a larger formula.
See a doctor if your sore throat or cough has not improved after about five days, or if it keeps coming back.
Get medical help the same day if you develop severe throat pain with a high fever, cannot swallow your own saliva, have a swollen neck, or your voice becomes muffled.
Stop taking it and contact a doctor promptly if you notice puffy ankles or face, unusual muscle weakness or cramps, a fluttering or racing heartbeat, a sharp rise in blood pressure, or you are passing much less urine than normal.
Call emergency services if you have trouble breathing, cannot swallow, or you faint or have chest pain with an irregular heartbeat.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Kanzoto is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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