Xiang Ru San — Mosla Powder

On this page

1. Overview
2. TCM pattern
3. Key herbs
4. Formula actions
5. Conditions treated
6. Comparisons with related formulas
7. Modifications
8. Cautions

Overview

Xiang Ru San — Mosla Powder — is a Song-dynasty formula from the official pharmacopoeia Tai Ping Hui Min He Ji Ju Fang (1078). It is the classical formula for the very specific summer-time pattern of being exposed to summer heat outside but then chilled by cold (air conditioning, cold drinks, sudden rain) so that an external Cold layer traps an internal Heat-Damp pathogen.

The name “Xiang Ru” (literally “fragrant softness”) refers to the chief herb Xiang Ru (Mosla chinensis), an aromatic mint-family plant that disperses the surface and transforms summer Damp. The formula is sometimes called “the Ma Huang Tang of summer” because it does for summer-cold what Ma Huang Tang does for winter-cold — release the exterior — but with a milder, more aromatic action suited to the season.

In modern practice this formula is given in summer for the common picture of someone who has been at the beach or working in heat, gets caught in an air-conditioned room or has a cold drink, and develops a sudden fever, no sweating, headache, body aches and an upset stomach. It is also used for true heatstroke in its early stage, alongside cooling and rehydration.

I prescribe Xiang Ru San as part of bespoke herbal formulas from pharmaceutical-grade granules sourced from Sun Ten in Taiwan.

TCM pattern

Xiang Ru San is prescribed for summer-heat with external Wind-Cold and internal Damp:

• Acute onset in summer or hot weather with a clear cold-exposure trigger
• Fever with chills and no sweating
• Headache — heavy, frontal or whole-head
• Body aches and heaviness
• Nausea, vomiting, abdominal pain
• Loose stools or watery diarrhoea
• Thirst with desire for cold drinks
• Aversion to cold and feeling stuffy
• No appetite
• Tongue — thick white or slightly yellow greasy coat
• Pulse — floating, slightly rapid

Key herbs

1. Xiang Ru (Mosla chinensis) — chief; aromatic; releases the surface and transforms summer Damp
2. Hou Po (Magnolia officinalis) — transforms Damp and moves Qi in the middle burner
3. Bai Bian Dou (Lablab purpureus) — transforms summer-Damp and strengthens the Spleen

Formula actions

1. Releases the exterior
2. Transforms summer Damp
3. Harmonises the middle burner
4. Resolves Damp in the Spleen

Conditions treated

1. Summer flu / summer cold with sudden cold exposure and stuck Heat-Damp
2. Heatstroke (early stage) alongside conventional cooling and rehydration
3. Acute gastroenteritis in summer with nausea and vomiting and loose stools
4. Holiday-related digestive upset with mixed travel exposures
5. Sunstroke recovery
6. Air-conditioning-related summer illness

Comparisons with related formulas

• Huo Xiang Zheng Qi San — broader formula for summer-Damp affecting the Spleen with diarrhoea and nausea; more focus on internal Damp.
• Liu Yi San — for pure summer-heat with thirst, dark urine, no exterior Cold layer.
• Yin Qiao San — for Wind-Heat exterior, not summer-Damp.
• Qing Shu Yi Qi Tang — for summer-heat damaging Qi and Yin with weakness and thirst.

Modifications

• For prominent fever and Heat signs, add Lian Qiao and Jin Yin Hua
• For prominent vomiting, add Huo Xiang and Ban Xia
• For prominent diarrhoea, add Huang Lian and Mu Xiang
• For Heat damage to Qi and Yin, combine with Qing Shu Yi Qi Tang principles

Cautions

Not appropriate for pure summer-Heat without exterior Cold — the warming Xiang Ru is contraindicated. Use Liu Yi San or Qing Shu Yi Qi Tang.

True heatstroke (body temperature >40°C, altered consciousness, no sweating) is a medical emergency — call 999. This formula is supportive only in early presentations.

Not appropriate in pregnancy without specialist supervision.

Always consult a qualified Chinese herbalist registered with the RCHM.

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