What is Ireito?

Ireito is a traditional Japanese herbal formula (Kampo) used for short bouts of watery diarrhoea and vomiting, the kind that comes with a stomach bug. It is also given for a bloated, heavy, sloshy feeling in the stomach with thirst and reduced urine output.

In Japan it is handled as a single drug (Kampo). That means the whole formula is one licensed prescription product with a fixed recipe, not a mixture you blend yourself. Its other name is Heiisan combined with Goreisan, because it joins two older formulas into one.

The honest evidence position: Ireito has a long and respected place in Kampo practice, but almost no modern human trial evidence of its own. Long traditional use tells you that people have relied on something; it is not proof that it works. Both facts are true at the same time, and this page keeps them apart.

How does Ireito work?

Kampo explains Ireito as a formula that moves "stagnant water" out of the gut and back into normal circulation, while settling a stomach that feels damp and heavy. That is a traditional model of the body, not a description of measured biology.

Modern laboratory work on Goreisan, one of the two halves of Ireito, has looked at aquaporins (tiny water channels in cell membranes that let water cross). The idea is that the formula may change how water moves between the gut and the body. This work is in cells and animals, and it has not been confirmed as the reason people feel better.

The practical point is simpler. Nothing in Ireito replaces fluids and salts lost through diarrhoea and vomiting, and it is not an anti-infective (a medicine that kills germs).

What forms does Ireito come in?

You will most often meet Ireito as a dried extract granule or fine powder in a foil sachet. This is the standard Japanese prescription form and the form used in hospitals.

Other forms you may see: - Tablets or capsules of the same dried extract. - A loose mix of cut herbs to be simmered into a decoction (a strong tea made by boiling herbs in water). - Over-the-counter packs at lower strength in Japanese pharmacies.

Granules are usually stirred into hot water and drunk while warm.

Where it comes from:

Ireito comes from the Chinese formula Weiling Tang, recorded in Chinese medical texts from around the Ming period and earlier. It was built by joining two well-known formulas, Heiisan (Ping Wei San) and Goreisan (Wu Ling San).

It was adopted into Japanese Kampo, where it has been a standard prescription for acute upset stomach for centuries, and it is also used in Korean medicine as Wiryeongtang. That spread across several traditions is why its traditional standing is strong even though its trial record is thin.

What does Ireito help with?

• Acute gastroenteritis with watery diarrhoea and vomiting: This is the classic Kampo use and the reason Ireito is prescribed most often in Japan. Practitioners choose it when stools are watery rather than bloody, the person is thirsty, and urine output has dropped. Published human trial evidence for this use is very limited. Treat Ireito as a comfort measure beside fluids, not as a treatment for the infection itself.
• Watery diarrhoea with thirst and reduced urine: Tradition sees this pattern as water sitting in the gut instead of circulating, and Ireito is the standard answer. Clinically, this same pattern is an early sign of dehydration. That is the safety point: thirst plus little urine means you need fluids and salts first, and possibly a doctor, before you think about herbs.
• Bloating and a heavy, waterlogged stomach feeling: The Heiisan half of the formula was built for exactly this: a damp, full, sluggish stomach with a coated tongue and poor appetite. It is a long-standing traditional use. No controlled human trials support it. Persistent bloating deserves a medical check rather than repeated self-treatment.
• Indigestion after overeating or too much cold drink: Kampo texts describe Ireito for stomach upset brought on by cold food and drink or by eating too much. This is traditional practice and reported clinical experience. We found no trial evidence for this use.
• Mild leg swelling with digestive upset: Because Goreisan is used traditionally for fluid retention, Ireito is sometimes chosen when mild swelling accompanies stomach trouble. Be careful here. Ireito contains licorice, which can itself cause swelling and raise blood pressure, so swelling that appears or worsens while you take it is a reason to stop and get checked.

Which foods are rich in Ireito?

1. Licorice sweets and licorice root tea: a common hidden source of the same glycyrrhizin that is in this formula
2. Ginger: a culinary version of one of the formula's herbs
3. Cinnamon: the kitchen spice from the same bark family used here
4. Dried citrus peel: used as a seasoning in East Asian cooking

Practical Tips:

While taking Ireito, keep licorice sweets and licorice tea to a minimum, because the licorice load adds up.

What are the side effects of Ireito?

• Nausea or a heavy feeling in the stomach
• Loss of appetite
• Loose stools or, less often, constipation
• Skin rash, redness or itching
• Swelling of the face, hands or ankles
• Rising blood pressure
• Muscle weakness, cramps or unusual tiredness
• Low potassium (less potassium in the blood than your heart and muscles need)
• Rarely, muscle damage causing dark or cola-coloured urine
• Rarely, liver irritation showing as yellow skin or eyes, dark urine or pain under the right ribs
• Rarely, lung irritation causing a dry cough, fever and breathlessness

Good to know:

Most people who take Ireito for a few days have no trouble with it. The common problems are mild stomach upset or a rash.

The effect worth knowing about is pseudoaldosteronism (a licorice reaction in which the body holds on to salt and water and loses potassium, a mineral your heart and muscles need). It shows up as swelling, rising blood pressure, muscle weakness and cramps. It is more likely with higher doses, longer use, older age, or when several licorice-containing products are taken together.

Rare but serious reactions reported with licorice-containing Kampo formulas include muscle breakdown, liver injury and lung inflammation. These are uncommon, but they are the reason this page is not rated as routine.

How much Ireito should you take?

• Recommended daily: Typical adult use in Japan is about 7.5 g of the dried extract granules per day, split into two or three doses. Packs vary in strength, so follow the label or your prescriber rather than this number. Doses for children are lower and are worked out by age or body weight. Do not guess a child's dose at home. If you also take any other licorice-containing product, the licorice adds up across products. Tell your doctor or pharmacist so the total can be checked.
• Best time of day: Spread the daily amount over two or three doses across the day, at roughly even intervals. There is no evidence that any one time of day works better.
• With or without food: Traditionally taken before meals or between meals, on a fairly empty stomach, stirred into hot water. If it makes you feel queasy that way, taking it just after food is acceptable and will not ruin it.
• Time to effect: When it helps, people usually notice easier stools and less nausea within a day or two. If nothing has changed after about three days, it is not working for you.
• How long to take it: Ireito is meant for short-term use, usually a few days while an acute upset settles. Reassess after 3 to 5 days. If diarrhoea or vomiting has not improved in that time, stop and see a doctor. Longer courses raise the risk from licorice, and any use beyond a week or two should be supervised, with blood pressure and potassium checked.