Natural Herb Library

Cassia Bark Oil

Chinese
肉桂油
Pinyin
Rou Gui You
Latin
Oleum Cinnamomi
Botanical illustration of Cassia Bark Oil, Cinnamomum aromaticum, showing branch, leaves, bark, oil-rich inner bark, distilled oil, and diagnostic plant details.
Botanical plate by Kodi .

Known in TCM as Rou Gui You (肉桂油), this acrid and sweet, warm herb enters the Spleen and Stomach. Traditionally, it warms the middle burner and dispels interior cold - Rou Gui You is used when cold obstructs the Spleen and Stomach, leading to epigastric chilliness, poor appetite, abdominal pain, or loose stool that clearly improves with warmth, most often applied for abdominal pain, diarrhea, and indigestion. Modern research has identified trans-cinnamaldehyde among its active constituents.

Part used: Oil

Also Known As

Cinnamomi

Latin: Oleum Cinnamomi | Pinyin: Rou Gui You | Chinese: 肉桂油

TCM Properties

Taste
acrid, sweet
Temperature
warm
Channels
Spleen, Stomach

Traditional Use

Primary Actions

  • Warms the middle burner and dispels interior cold - Rou Gui You is used when cold obstructs the Spleen and Stomach, leading to epigastric chilliness, poor appetite, abdominal pain, or loose stool that clearly improves with warmth.
  • Strengthens Stomach and Spleen Yang in aromatic form - the oil preparation is lighter and more immediately dispersing than the crude bark decoction, so it is historically associated with short-term use for cold-damp digestive discomfort, nausea from cold, and sluggish middle-jiao Qi movement.
  • Expels wind and opens the surface through aromatic warmth - traditional summaries describe it as useful when exterior wind-cold or cold-damp lodges superficially while the middle burner is also weak and chilled.
  • Provides a concentrated warming external preparation - topical use is traditionally directed toward cold-pattern pain, localized chill, and stiff aching areas where a penetrating cinnamon preparation is preferred over a bulky decoction.

Secondary Actions

  • Rou Gui You should be understood as a preparation derived from the same source plant as Rou Gui, but in a much more concentrated aromatic form that is stronger on the nose, more irritating to tissues, and less suitable for prolonged unsupervised use.
  • The alternate name Gui Pi You (桂皮油) appears in some materia medica references and reflects the overlap between cassia bark and cinnamon-bark oil terminology in trade.

Classical References

  • TCM Wiki records Rou Gui You as pungent, sweet, and warm, with the actions of expelling wind, strengthening the Stomach, and warming the Spleen and Stomach.
  • Traditional usage treats the oil as a preparation-state derivative of Rou Gui rather than a different medicinal species, so its core therapeutic direction remains warming, dispersing, and middle-jiao supporting.
  • IDENTITY NOTE: this record is for the concentrated oil preparation 肉桂油, not the crude bark herb Rou Gui (肉桂); the two share source material but are not interchangeable gram-for-gram.

Modern Research

Active Compounds

  • trans-cinnamaldehyde (phenylpropanoid aldehyde) - the dominant cassia-oil constituent responsible for much of its antimicrobial, warming, and anti-inflammatory research interest
  • Eugenol (phenylpropanoid) - contributes aromatic, analgesic, and antimicrobial activity in cinnamon-type essential oils
  • Coumarin (benzopyrone) - an important safety-relevant constituent because higher cassia exposure can increase hepatotoxicity concerns
  • Cinnamyl acetate (aromatic ester) - part of the fragrant volatile fraction that helps distinguish cinnamon and cassia oils organoleptically
  • Cinnamic acid and related phenylpropanoids - support the broader antioxidant and metabolic pharmacology literature around cinnamon oils

Studied Effects

  • Direct antimicrobial testing found Chinese cassia oil and cinnamaldehyde active against a range of bacterial and fungal targets, supporting the long-standing external and preservative interest in cinnamon oil preparations (PMID 16710900).
  • A Cinnamomum cassia essential-oil nano-emulsion showed antioxidant, antibacterial, and biologic antiproliferative activity in experimental systems, illustrating how modern formulation work is trying to improve the delivery of this volatile oil (PMID 35472756).
  • A recent pharmacology review summarizes cinnamon oil's chemical composition and discusses antimicrobial, anti-inflammatory, antioxidant, metabolic, and application-oriented research across multiple Cinnamomum oils, including cassia-rich preparations (PMID 39770541).

PubMed References

Safety & Interactions

Contraindications

  • Known cinnamon or cassia hypersensitivity
  • Undiluted application to damaged skin or mucous membranes
  • Marked internal Heat or Yin-deficiency heat patterns

Cautions

  • Cassia bark oil is more irritating and sensitizing than the crude bark herb and should generally be diluted before topical use
  • Some cinnamon products contain enough coumarin to raise hepatotoxicity concerns, especially with heavy or prolonged intake
  • Gastrointestinal upset, burning sensations, and allergic skin reactions are possible with concentrated cinnamon oils

Drug Interactions

  • CYP450 substrate drugs … Preclinical studies suggest cinnamon inhibits CYP2A6, CYP2C9, CYP2D, and CYP3A4 and may increase the risk of side effects from drugs metabolized by these enzymes (Moderate) Source: Memorial Sloan Kettering Integrative Medicine - Cinnamon
  • Statins … Concurrent use has been associated with hepatitis in a case report (Moderate) Source: Memorial Sloan Kettering Integrative Medicine - Cinnamon
  • Pioglitazone … Animal studies suggest cinnamon can increase pioglitazone bioavailability (Moderate) Source: Memorial Sloan Kettering Integrative Medicine - Cinnamon

Conditions

Frequently Asked Questions

What is Cassia Bark Oil used for?

Cassia Bark Oil is traditionally used to Warms the middle burner and dispels interior cold - Rou Gui You is used when cold obstructs the Spleen and Stomach, leading to epigastric chilliness, poor appetite, abdominal pain, or loose stool that clearly improves with warmth., Strengthens Stomach and Spleen Yang in aromatic form - the oil preparation is lighter and more immediately dispersing than the crude bark decoction, so it is historically associated with short-term use for cold-damp digestive discomfort, nausea from cold, and sluggish middle-jiao Qi movement., Expels wind and opens the surface through aromatic warmth - traditional summaries describe it as useful when exterior wind-cold or cold-damp lodges superficially while the middle burner is also weak and chilled., Provides a concentrated warming external preparation - topical use is traditionally directed toward cold-pattern pain, localized chill, and stiff aching areas where a penetrating cinnamon preparation is preferred over a bulky decoction.. Research has investigated its effects on: Direct antimicrobial testing found Chinese cassia oil and cinnamaldehyde active against a range of bacterial and fungal targets, supporting the long-standing external and preservative interest in cinnamon oil preparations (PMID 16710900).; A Cinnamomum cassia essential-oil nano-emulsion showed antioxidant, antibacterial, and biologic antiproliferative activity in experimental systems, illustrating how modern formulation work is trying to improve the delivery of this volatile oil (PMID 35472756)..

What are other names for Cassia Bark Oil?

Cassia Bark Oil is also known as Cinnamomi. In TCM: 肉桂油 (Rou Gui You); Oleum Cinnamomi.

Is Cassia Bark Oil safe during pregnancy?

The safety of Cassia Bark Oil during pregnancy has not been established. Consult a qualified healthcare provider before use.

What are the contraindications for Cassia Bark Oil?

Cassia Bark Oil should not be used in: Known cinnamon or cassia hypersensitivity; Undiluted application to damaged skin or mucous membranes; Marked internal Heat or Yin-deficiency heat patterns. Consult a qualified practitioner before use.

Does Cassia Bark Oil interact with any medications?

Cassia Bark Oil may interact with: CYP450 substrate drugs - Preclinical studies suggest cinnamon inhibits CYP2A6, CYP2C9, CYP2D, and CYP3A4 and may increase the risk of side effects from drugs metabolized by these enzymes - (Moderate severity); Statins - Concurrent use has been associated with hepatitis in a case report - (Moderate severity); Pioglitazone - Animal studies suggest cinnamon can increase pioglitazone bioavailability - (Moderate severity). Always inform your healthcare provider of any herbal supplements you are taking.