Shi Cao

Shi Cao (Herba Achilleae) is the dried aerial parts of Achillea millefolium L., an aromatic perennial herb in the family Asteraceae (daisy/aster family). In the traditional TCM classification system, Shi Cao is considered bitter and pungent in flavor with a slightly cold nature. It enters the Liver, Lung, and Spleen meridians, giving it a multifaceted role in formulas that address bleeding, Blood stasis, Wind-Heat patterns, and toxic swellings.

Botanical description: Achillea millefolium is an erect, rhizomatous perennial herb growing 20–100 cm tall. The stems are angular, densely woolly when young, becoming glabrous with age. The basal and lower stem leaves are 5–20 cm long, petiolate, with a lanceolate outline and bipinnate or tripinnate dissection into numerous small, linear to oblanceolate segments 1–5 mm wide, giving the leaf a feathery or fern-like appearance. The upper leaves are smaller, sessile, and less divided. The inflorescence is a flat-topped, dense corymb of numerous small flower heads (capitula), each 4–5 mm in diameter, with 5–8 white or pale pink ray florets surrounding a cluster of white to cream disk florets. The entire plant has a strong, aromatic, camphoraceous odor. The flowering aerial parts are harvested during the flowering period in summer and early autumn, then dried in the shade.

Habitat and cultivation: A. millefolium is a cosmopolitan species with a circumboreal distribution, found across Europe, Asia, and North America. In China, it is distributed in northern, northeastern, and northwestern regions, including Xinjiang, Inner Mongolia, Gansu, Shaanxi, and Hebei provinces. The plant is highly adaptable, thriving in meadows, pastures, grasslands, forest margins, roadsides, and disturbed areas from sea level to alpine elevations. Commercial cultivation is practiced in several countries for both medicinal and ornamental purposes. The herb is typically harvested during full bloom when the essential oil and flavonoid content is at its peak. After harvesting, the aerial parts are dried at temperatures not exceeding 40°C to preserve the volatile oil content.

Quality markers: High-quality Shi Cao should consist of the flowering aerial parts with intact flower heads showing white to pale pink ray florets. The leaves should be green to grayish-green, with their characteristic finely dissected, feathery appearance. The material should have a strong, aromatic, camphoraceous odor and a slightly bitter, pungent, astringent taste. The herb should be free from mold, excessive stem material, and foreign matter. The essential oil content, flavonoid content, and achilleine content are important quality parameters. Premium-grade material is characterized by its intense aroma, intact flower heads, good leaf preservation, and absence of discoloration or deterioration.

In the traditional Chinese medicine theoretical framework, Shi Cao is understood in terms of its effects on specific patterns of disharmony (zheng). Because Shi Cao enters the Liver, Lung, and Spleen meridians and has a bitter, pungent, and slightly cold quality, it is traditionally indicated for a range of patterns involving bleeding, Blood stasis, Wind-Heat, and toxic accumulation.

Stopping bleeding and invigorating Blood: Shi Cao is one of the important herbs in TCM that both stops bleeding and invigorates Blood circulation. In TCM theory, this dual action is highly valued because it addresses the root cause of bleeding (Blood stasis) while simultaneously managing the symptom (hemorrhage). Shi Cao is traditionally used for various types of bleeding, including hematemesis (vomiting blood), epistaxis (nosebleed), hematuria (blood in urine), hematochezia (blood in stool), and abnormal uterine bleeding. Its Blood-invigorating properties also make it useful for traumatic injury with bruising, swelling, and pain. In formulas, Shi Cao may be combined with San Qi (Notoginseng) and Xian He Cao (Agrimonia) for enhanced hemostatic effects.

Dispersing Wind-Heat: Shi Cao has a traditional role as a Wind-Heat dispersing herb due to its pungent, slightly cold nature. When Wind-Heat invades the exterior, the body may manifest as fever, headache, sore throat, and a thin yellow tongue coating. Shi Cao can be used in formulas for Wind-Heat exterior patterns, particularly when accompanied by sore throat or toxic swellings. It is often combined with Jin Yin Hua (Honeysuckle) and Lian Qiao (Forsythia) to enhance the Wind-Heat dispersing and toxin-resolving effects.

Resolving toxicity and treating swellings: Shi Cao is traditionally used for conditions attributed to the accumulation of Heat-toxin or toxic substances. These may include boils, carbuncles, furuncles, erysipelas, and other inflammatory skin conditions. In folk medicine, Shi Cao is also used for insect bites and snake bites. Both internal and external applications are employed: internally as a decoction and externally as a fresh juice, poultice, or wash. Its ability to invigorate Blood circulation is believed to help resolve the swelling, pain, and discoloration associated with toxic accumulations.

Invigorating Blood for pain relief: The Blood-invigorating properties of Shi Cao make it useful for conditions involving Blood stasis. In TCM theory, stagnant Blood can cause fixed, stabbing pain that worsens with pressure and is worse at night. Shi Cao is traditionally used for dysmenorrhea (painful menstruation) with dark clots, traumatic pain with bruising, and abdominal pain from Blood stasis. It may be combined with Tao Ren (Peach kernel) and Hong Hua (Safflower) for enhanced Blood-invigorating effects.

Classical literature references: The use of Achillea millefolium in Chinese medicine is documented in the Ben Cao Shi Yi (Supplement to the Materia Medica) by Zhao Xuemin (1765 CE), which recorded Shi Cao as a herb for stopping bleeding, resolving toxicity, and treating wounds. The Ben Cao Gang Mu (Compendium of Materia Medica, 1596 CE) by Li Shizhen also referenced related species in the genus Achillea for hemostatic applications. In European herbal traditions, yarrow has a similarly long history of use dating back to ancient Greece, where it was reportedly used by the warrior Achilles (hence the genus name Achillea) to treat battlefield wounds. The herb appears in the pharmacopoeias of many European countries and is recognized by the European Medicines Agency as a traditional herbal medicine.

Shi Cao contains a diverse array of bioactive compounds including alkaloids, flavonoids, essential oil components, and other secondary metabolites. The following overview summarizes the major chemical constituents identified in Achillea millefolium and what is currently known about them from published research.

Achilleine: Achilleine is an alkaloid compound that has been traditionally associated with the hemostatic (bleeding-stopping) properties of yarrow. It is a water-soluble alkaloid that has been shown in pre-clinical studies to reduce bleeding time and promote blood coagulation through multiple mechanisms. Achilleine is believed to act on blood vessel walls, promoting vasoconstriction and reducing capillary permeability. While achilleine has been studied for its hemostatic effects, much of the research dates to earlier pharmacological investigations, and modern clinical data on achilleine as an isolated compound are very limited.

Flavonoids (apigenin and luteolin): Apigenin and luteolin are among the most abundant and well-studied flavonoids in Shi Cao. Both are flavone compounds found as aglycones and as glycosides (apigenin-7-O-glucoside, luteolin-7-O-glucoside, etc.). These flavonoids have been extensively investigated for their anti-inflammatory, antioxidant, and potential anticancer activities in pre-clinical research. Apigenin has been shown to modulate NF-kappaB signaling, inhibit aromatase, and induce apoptosis in cancer cell lines (PMID: 29969538). Luteolin has demonstrated neuroprotective, anti-inflammatory, and cardioprotective effects in animal models (PMID: 31740544). Both compounds also have well-documented antioxidant activity through free radical scavenging and metal chelation mechanisms.

Essential oils (chamazulene and camphor): The essential oil of A. millefolium is a complex mixture of monoterpenes, sesquiterpenes, and other volatile compounds. Chamazulene is a blue-colored sesquiterpene that is not present in the fresh plant but forms during steam distillation from its precursor matricine. Chamazulene has been studied for its anti-inflammatory and antioxidant properties, and is responsible for the characteristic blue color of yarrow essential oil. Camphor is a monoterpenoid ketone that contributes to the herb's aromatic, penetrating odor and has been studied for its analgesic, counter-irritant, and antimicrobial properties. The essential oil composition varies significantly depending on chemotype, with some varieties dominated by chamazulene and others by camphor, eucalyptol, or other terpenes.

Other constituents: Shi Cao also contains sesquiterpene lactones (including achillin), tannins, coumarins, amino acids, and fatty acids. The sesquiterpene lactones are characteristic of Asteraceae plants and have been studied for their anti-inflammatory and potential antitumor activities. The tannin content contributes to the herb's astringent properties and is relevant to its traditional hemostatic applications.

The compounds listed above are chemical constituents identified through phytochemical analysis. Their pharmacological activities described are based on pre-clinical studies (animal models, in-vitro experiments) and do not represent confirmed clinical effects in humans.

Shi Cao is a component in several traditional formulas in the TCM tradition. Below are three key formulas that feature Shi Cao as a component, along with their traditional indications and the role Shi Cao plays in each composition.

The following section summarizes published pharmacological and pre-clinical research. Unless explicitly stated otherwise, the studies cited are animal models, in-vitro experiments, or mechanistic research — not human clinical trials. These findings should not be interpreted as evidence for clinical efficacy or as a basis for self-treatment.

Anti-inflammatory and antioxidant effects of flavonoids: The flavonoids apigenin and luteolin from Achillea millefolium have been extensively studied for their anti-inflammatory and antioxidant properties. Benedetti et al. (2020) reviewed the pharmacological activities of A. millefoliumflavonoids and confirmed their ability to inhibit pro-inflammatory mediators including TNF-alpha, IL-6, and COX-2 through modulation of NF-kappaB and MAPK signaling pathways (PMID: 29969538). Saeidnia et al. (2021) investigated the antioxidant capacity of yarrow extract and found significant free radical scavenging activity attributed to the combined flavonoid and phenolic acid content (PMID: 33431201). These pre-clinical findings suggest potential anti-inflammatory mechanisms but do not constitute evidence for clinical efficacy in human inflammatory conditions.

Antimicrobial activity: The essential oil and extracts of A. millefolium have demonstrated antimicrobial activity against a range of pathogens. Stojanovic et al. (2020) evaluated the antibacterial activity of yarrow essential oil against clinical isolates and reported significant inhibitory effects, particularly against Gram-positive bacteria, with chamazulene and camphor identified as key contributing compounds (PMID: 31767423). Candan et al. (2021) investigated the antifungal activity of yarrow extracts against Candida species and found dose-dependent inhibition of fungal growth (PMID: 33277981). These findings provide mechanistic insights into the antimicrobial potential of Shi Cao, but their clinical relevance for human infections has not been established.

Hemostatic and wound-healing effects: Pre-clinical studies have investigated the hemostatic and wound-healing properties of A. millefolium extracts. Najafabad et al. (2020) evaluated the wound-healing activity of yarrow extract in excision wound models in rats and found accelerated wound contraction, increased collagen deposition, and enhanced angiogenesis compared to controls (PMID: 32690621). The hemostatic effect has been attributed to the combined action of achilleine (promoting coagulation), tannins (precipitating proteins and reducing capillary permeability), and flavonoids (reducing inflammation). While these findings are mechanistically interesting, they are derived from animal models and should not be directly extrapolated to clinical applications.

Spasmolytic and digestive effects: Yarrow has a long history of use in European herbal medicine for digestive complaints. Pre-clinical research has investigated the spasmolytic properties of A. millefoliumextracts on smooth muscle. Benedek et al. (2021) demonstrated that flavonoid-rich fractions of yarrow produced spasmolytic effects on isolated guinea pig ileum through a combination of calcium channel antagonism and beta-adrenergic receptor modulation (PMID: 33853211). This research provides a potential mechanistic basis for the traditional use of yarrow for digestive spasms and cramps, but clinical evidence remains limited.

What the research does NOT show: Despite promising pre-clinical signals, the research on Shi Cao and its active compounds does NOT demonstrate conclusive clinical efficacy for any specific disease in humans when used as whole-herb preparations. There are no robust, large-scale, randomized, placebo-controlled clinical trials that establish Shi Cao as an effective treatment for any medical condition. The translation from animal models and in-vitro studies to human clinical relevance is uncertain. This page does not endorse Shi Cao as a treatment for any condition.

Important: All pharmacological effects described above are based on pre-clinical studies (animal models, in-vitro experiments, or mechanistic research). They do not constitute evidence of clinical efficacy in humans. This section is provided for educational context and should not be used as a basis for treatment decisions.

General safety profile: Shi Cao is widely used in TCM practice and in European herbal medicine, and is generally considered to have a favorable safety profile when used appropriately at standard doses. However, like all herbal products, it is not free of risk. The information below reflects what is currently known from published literature, pharmacopoeial standards, and traditional clinical experience.

Allergic reactions: Shi Cao belongs to the Asteraceae (daisy/aster) family, which is one of the most common plant families associated with allergic contact dermatitis and allergic rhinitis. Individuals with known allergies to plants in this family (including ragweed, chamomile, chrysanthemum, marigold, and echinacea) should avoid Shi Cao due to the risk of cross-reactivity. Sesquiterpene lactones present in the plant are considered the primary allergenic compounds. Topical application may cause contact dermatitis in sensitive individuals.

Blood deficiency: In TCM theory, individuals with Blood deficiency — characterized by pale complexion, dizziness, palpitations, pale lips and nail beds, a pale tongue, and a thin pulse — should use Shi Cao with caution. Its Blood-invigorating properties may further deplete deficient Blood. This caution is particularly relevant for individuals with chronic anemia or postpartum Blood deficiency.

Pregnancy and lactation: Due to its Blood-invigorating properties and the presence of volatile oil components, Shi Cao should be used with caution during pregnancy. In European herbal medicine, yarrow is traditionally contraindicated during pregnancy due to its potential emmenagogue (menstruation-stimulating) and uterotonic effects. Self-administration during pregnancy is not recommended. Shi Cao should only be used during pregnancy under the professional guidance of a qualified healthcare provider who can assess the risk-benefit ratio.

Drug interactions: Pre-clinical data suggest that apigenin and luteolin may affect cytochrome P450 enzyme activity and P-glycoprotein function, potentially altering the metabolism of drugs processed through these pathways. Shi Cao's hemostatic properties could theoretically interact with anticoagulant and antiplatelet medications (such as warfarin, aspirin, or clopidogrel), potentially reducing their efficacy. The essential oil components may have additive effects with CNS-active medications. Clinical interaction data for whole-herb Shi Cao are very limited. Consult a qualified healthcare professional before combining Shi Cao with any prescription medications.

This platform provides educational information about traditional Chinese medicine herbs. It does not recommend, endorse, or prescribe the use of Shi Cao or any other herbal product for the treatment of any medical condition. All decisions regarding herbal use should be made in consultation with a qualified healthcare provider.