What is Xiang Su San?

Xiang Su San is a classic Chinese herbal formula taken at the very start of a common cold, especially when the cold comes with a tight, blocked or bloated feeling in the chest and stomach. It is catalogued here as a single drug (TCM formula) and is also known as Cyperus and Perilla Leaf Powder.

It is a four-herb mix: xiang fu (cyperus rhizome), zi su ye (perilla leaf), chen pi (dried tangerine peel) and zhi gan cao (honey-fried licorice root). It is usually sold as a loose powder, a granule sachet or a decoction (a tea made by simmering the herbs).

The honest evidence verdict: this is a well-documented staple of Chinese herbal practice, but we could not find published human trials of the formula itself. Long traditional use tells you what people have done with a remedy, not that it works; that point applies to everything below and is not repeated.

How does Xiang Su San work?

In traditional Chinese medicine terms, the formula is said to "release the exterior" (push out an early cold) while moving stagnant qi in the digestive tract. That is a traditional model, not a tested biological mechanism.

In modern terms, the plausible parts are simple. Perilla leaf and tangerine peel contain aromatic oils that may relax gut muscle and ease wind, and warm liquid itself soothes a sore, blocked nose and throat.

None of this has been confirmed for the finished formula in people. Treat any mechanism story you read about Xiang Su San, including this one, as a hypothesis.

What forms does Xiang Su San come in?

Loose powder, the original form, mixed into warm water and drunk as a suspension.

Granule sachets, which dissolve in hot water. Raw dried herbs, simmered at home into a decoction (a strong tea). Ready-made pills or capsules, less common for this formula.

Strengths vary a lot between makers, so always follow the label on the product in your hand rather than a number from a book.

Where it comes from:

Xiang Su San appears in the Tai Ping Hui Min He Ji Ju Fang, a Song dynasty government formulary published in the early 12th century. It has stayed in continuous use in Chinese herbal practice ever since.

It was written for the person who catches a chill and also feels food stuck and bloated. Later Chinese and Japanese Kampo texts kept it and built variations on it.

What does Xiang Su San help with?

• Early-stage common cold with chills: This is the formula's main traditional use, for the first day or two of a cold when you feel chilly, achy and blocked in the nose. Chinese texts have prescribed it this way for roughly 900 years. We found no human trials of Xiang Su San for colds. Nothing here tells you it shortens a cold or prevents one.
• Cold or flu-like illness with stomach bloating and poor appetite: Tradition treats this combination as the formula's exact target: a chill on the outside plus stuck digestion underneath. Tangerine peel and cyperus are the herbs credited with the digestive part. Evidence is traditional only. No published trial has measured bloating or appetite in people taking this formula.
• Blocked, stuffy feeling in the chest and upper abdomen: Practitioners describe this as "qi stagnation" and consider the formula a mild, gentle mover. The aromatic oils in perilla and citrus peel are the usual modern explanation offered. That explanation has not been tested for this formula in people. If chest tightness is new, severe or comes with breathlessness, treat it as a medical problem and not a herb problem.
• Mild nausea during a cold: Perilla leaf has a traditional reputation for settling the stomach, and the formula is sometimes chosen when a cold comes with queasiness. The evidence here is limited to tradition and to laboratory work on perilla constituents. It has not been shown to control nausea in a clinical study.
• Morning sickness (traditional claim only, and not advised): Some older Chinese sources mention perilla-based formulas for nausea in pregnancy. We list this only because you may read it elsewhere. Do not act on it. The formula contains licorice, which is linked in research to worse outcomes in pregnancy, so this library advises against use in pregnancy entirely.

Which foods are rich in Xiang Su San?

1. Shiso (perilla) leaf: the same leaf used in the formula, eaten fresh in Japanese and Korean cooking
2. Dried tangerine or orange peel: used as a cooking spice in Chinese dishes and in marmalade
3. Licorice sweets and licorice tea: contain glycyrrhizin, the same compound that drives this formula's blood pressure and potassium risks

Practical Tips:

Eating shiso or citrus peel as food is not the same as taking the formula, but heavy licorice sweet eating does add to the same risk.

What are the side effects of Xiang Su San?

• Stomach upset or mild nausea
• Loose stools
• Rash or itching in people allergic to mint-family or citrus plants
• Raised blood pressure, from the licorice, with heavy or long use
• Low potassium (hypokalaemia), from the licorice, with heavy or long use
• Ankle or facial swelling from fluid retention
• Headache or tiredness that can come with low potassium

Good to know:

Short-term use of a normal dose is generally well tolerated, and most reported problems are mild stomach upset. The serious risks all trace back to one ingredient: honey-fried licorice root.

Licorice taken in large amounts or over weeks can raise blood pressure, drive potassium down and cause fluid retention, and very low potassium can disturb heart rhythm. This is why the formula is rated caution rather than routine.

How much Xiang Su San should you take?

• Recommended daily: There is no dose established by modern research. Classical practice used about 6 to 9 g of the powder per dose, taken two or three times a day in warm water. Modern granule products vary widely in strength. Follow the label on your product, or the amount a qualified practitioner gives you, rather than a figure from an old text. Because of the licorice content, do not double up on dose to "push through" a cold.
• Best time of day: Traditionally taken warm, two or three times through the day, with the first dose as soon as the chills start. Avoid a dose close to bedtime if warm drinks keep you awake.
• With or without food: Usually taken between meals with warm water, though taking it after food is fine if it upsets your stomach.
• Time to effect: Traditional use expects some easing of chills and stuffiness within a few hours to a day. This timing comes from practice reports, not from measured trials.
• How long to take it: Traditionally it is taken only while early cold symptoms last, which is usually three to five days. Stop once you feel better. See a doctor if you are no better after a week, or if you get worse at any point. Do not take it daily for weeks on end without medical advice, because the licorice in it can build up its effect on blood pressure and potassium.