What Liu Yi San is for
The skin picture is the eruption of hot, humid weather: prickly heat, heat rash and small hot lesions that itch and sting, with the surface feeling heated rather than dry. The explanation is Heat that Dampness holds at the surface, and the formula clears the Heat and drains the Dampness in one movement, six parts to one. It is a short summer course rather than a treatment for chronic skin disease.
The rash arrives with the weather. Small itchy papules or a fine red eruption appear, the skin feels prickly and hot, and the discomfort rises with the humidity. This is the heat rash of summer rather than an eczema that runs through the year, and the skin looks heated rather than dry or scaly. There may be a general sense of heat with it. In a child with a febrile rash, or where an eruption is severe, medical assessment comes first.
The tradition reads the rash as Heat that cannot leave because Dampness holds it at the surface. Hua Shi, six parts of the formula, clears the Heat and drains the Dampness downward so the Heat has a route out with it; Gan Cao in a small dose protects the middle, so that drainage does not injure the digestion. The six-to-one ratio is the whole design: enough draining to clear the eruption, and just enough sweetness to keep it from being too harsh. The same powder can be dusted on the skin as well as taken in water.
It is short term, for a few days to two weeks while the hot weather lasts, and it is not a treatment for chronic skin disease. Cold deficiency is excluded, and so is Yin deficiency without Dampness, where the skin is dry and thin and there is nothing to drain. Chickenpox in a child needs medical assessment rather than a dusting powder.
Actions
- Clears summer Heat
- Drains Dampness through the urine
- Relieves thirst and restlessness
- Soothes heat rashes and prickly heat
Properties
- Taste and temperature: Predominantly sweet and bland with a cold quality. Sweet and bland drain Dampness, cold clears Heat.
- Organs: Heart, Stomach, Bladder
- Channels: Heart, Stomach, Bladder
The pattern behind it
The pattern is summer Heat with Dampness. The Heat produces the thirst, the restlessness and the heat rash, and the Dampness keeps the Heat from clearing. The formula drains the Dampness out through the urine so the Heat can leave with it.
Composition
The herbs in Liu Yi San, with their role and dose.
| Role | Herb | Dose | Properties | Why it is there |
|---|---|---|---|---|
| Assistant | Hua Shi | 18 g | Cold, Sweet, bland | Clears Heat and drains Dampness through the urine, the large part of the ratio. |
| Gan Cao | 3 g | Neutral, Sweet | Protects the middle and prevents the draining from injuring digestion, the small part of the ratio. |
Patterns it treats
Summer Heat with Dampness
Prickly heat and heat rash in hot humid weather, with itchy papules and skin that feels heated rather than dry. The Heat is held at the surface by Dampness, so it cannot clear until the Dampness is drained.
How the formula is built
Six parts draining to one part protecting. The proportion is the formula: enough Hua Shi to clear the Heat and move the Dampness, and just enough Gan Cao to keep it from being too draining.
Skin conditions it is used for
Where this formula appears in the skin conditions of the library.
Preparation and use
Taken as a powder in warm or cool water, or applied topically as a dusting powder, under direction.
Modifications
- For summer heat with thirst, taken in water.
- For prickly heat, applied topically as a powder.
- If the Heat is marked, cooling herbs are added.
- If the person is depleted, the dose is reduced.
Timing
Taken in divided doses in water, or applied topically.
Duration
Short term: a few days to two weeks in hot weather.
Diet while taking it
Cool fluids; avoid hot spicy food.
Safety
Contraindications
Avoid in cold deficiency and in Yin deficiency without Dampness. Do not use for prolonged periods.
Interactions
Gan Cao may interact with diuretics, digoxin and corticosteroids. The draining action can add to diuretic medication.
Pregnancy
Generally considered low risk but use with professional guidance in pregnancy.
Breastfeeding
Use only under professional guidance.
Children
Used in children with reduced dose for prickly heat and summer heat.
Before you use it
Recorded from the classical record and rewritten in this project's own words. Educational only: not a prescription, and a febrile rash or severe heat illness needs urgent medical assessment.
General safety references
General references for herbal hepatotoxicity and herb-drug interactions; they are not specific to this formula.
- Review article: Herbal hepatotoxicity - an update on traditional Chinese medicine preparations. Alimentary Pharmacology & Therapeutics, 2014. PMID: 24844799.
- Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs, 2009. PMID: 19719333.
- Warfarin and food, herbal or dietary supplement interactions: a systematic review. British Journal of Clinical Pharmacology, 2021. PMID: 32478963.
Origin and history
Shang Han Biao Ben (伤寒标本) by Liu Wansu, Jin dynasty, 12th century.
Liu Yi San comes from Liu Wansu, the Jin dynasty physician who emphasised Heat as a cause of disease. Its name records the ratio of its two herbs, and it became the standard household formula for summer heat and prickly heat.
Classical record
The formula is recorded as two herbs in a six-to-one ratio for summer Heat with Dampness, clearing the Heat and draining the Dampness together.
Shang Han Biao Ben, Liu Wansu, Jin dynasty, as recorded in the classical record.
Evidence note
No controlled trial of this treatment in skin conditions was identified for this entry. What is described here rests on the classical and later materia medica record and on traditional clinical use, not on controlled trial evidence, and it is not a prediction of benefit. Where skin-specific research does exist it is linked above.
Common questions
What does the name mean?
Six to one, the ratio of the two herbs. The proportions are the formula.
Can it be used on the skin?
Yes, it is applied topically as a dusting powder for prickly heat and heat rash, under direction.
Can it be used for chickenpox?
Only for mild cases with summer-heat signs, and chickenpox in a child needs medical assessment.
Who should avoid it?
People with cold deficiency or Yin deficiency without Dampness.