Educational information, not medical advice — ask your doctor or midwife.
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.
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.
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.
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.
See a doctor if your cold is no better after a week, if a fever goes above 39C (102F), or if you become breathless, wheezy or cough up blood.
Stop the formula and get medical advice if your ankles or face swell, if you get bad headaches, or if you feel unusually weak or tired, since these can be signs of low potassium (hypokalaemia).
Get urgent help for chest pain, a pounding or irregular heartbeat, fainting, or a spreading rash with swelling of the lips or tongue.
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 Xiang Su San 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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