Yarrow as a Poultice
August 2001; Volume 4; 91-94
By Susan T. Marcolina, MD
Yarrow, or achillea millefolium, is a perennial herb in the Asteraceae (daisy) family. Native to Europe and western Asia, yarrow grows to approximately 3 feet in height during the summer months. It has dense clusters of white flower heads on flat-topped umbrella-like stalks with finely divided, fern-like leaves.1
Although yarrow has a hallowed medicinal history, there are very few scientific data to support more than its botanical use.
Historical Use
Yarrow has been used throughout history for its hemostatic, analgesic, and anti-inflammatory effects.
More than 2,500 years ago, Chinese physicians used Asian yarrow to treat inflammation, bleeding, and menstrual disorders, as well as dog and snake bites. According to legend, the Greek warrior Achilles used the herb to staunch the bleeding of battle wounds.2 Dioscorides, a Roman physician, also used the crushed plant on wounds, and its popular nicknames—herbe militaire, Soldier’s woundwort, and bloodwort—arose from this use. More recently, the colonists introduced yarrow to North America and the native Indians adopted it as an external treatment for wounds, burns, and sprains, as well as an internal treatment for arthritis, colds, and indigestion. Today, yarrow is used primarily as an ornamental plant and a mosquito repellent in flower gardens.3
Taxonomy
There has been considerable confusion about the taxonomic classification of yarrow and its chromosomal characteristics, which are associated with differences in the chemical composition of its flowers and leaves.4 There are several Achillea species, which differ in their ploidy (chromosome numbers) and cannot be distinguished morphologically. The normal chromosome number for achillea is 9. Therefore, the diploid number is 18. There also are tetraploid (2n = 36), hexaploid (2n = 54) and octaploid species (2n = 72). Table 1 summarizes the most commonly recognized species and their general properties.
| Table 1: Achillea species | |||
| Species Name | Chromosome Number & Ploidy |
Characteristics of Essential Oils |
Location |
|
|
|||
| A. millefolium | Hexaploid 2n = 54 | Low to zero proazulene content; contains thujone | Central and northern Europe (native); North America (introduced) |
| A. lanulosa | Tetraploid 2n = 36 | Up to 50% proazulene | Eastern Canada, New England (native) |
| A. collina | Tetraploid 2n = 36 | Up to 50% proazulene | Europe, western Asia |
| A. pannonica | Octaploid 2n = 72 | Low to zero proazulenes; contains thujone | Europe, western Asia |
| A. borealis | Hexaploid 2n = 54 | Low to zero proazulenes; contains thujone | West coast North America from California to Alaska, Arctic, Subarctic |
| A.
setacea, A. aspleniifolia |
Diploid 2n = 18 | Low to zero proazulenes; contains thujone | Europe, western Asia |
| A.
distans, A. stricta |
Hexaploid 2n = 54 | Low to zero proazulenes; contains thujone | Europe, western Asia |
|
|
|||
| Adapted from: Biste C. Cytotaxonomic studies of the group Achillea millefolium in East Germany. Feddes Repert 1977;88:53-61. | |||
|
|
|||
Other factors that influence the chemical composition of yarrow include climate, soil conditions, stage of flower development at harvest, and the time during the growing season at which the plant material is collected.5 Further complicating matters, polymorphisms occur within a particular species that change the chemical composition. The species most often referenced in the clinical literature is Achillea millefolium, and subsequent references to yarrow indicate this species.
Since these taxonomic categories of yarrow were not fully acknowledged by researchers until the mid 1970s, the literature available on yarrow is confusing and has conflicting findings, probably because investigators were working with different plant species. Because of these nosological problems, clinical studies refer to a voucher specimen to confirm the genetic identity of the plant used.3,6
Chemical Constituents
The crushed leaves and flowers of yarrow contain several biologically active compounds that would support its use in the healing of wounds. Chemists have studied the volatile essential oil of yarrow, obtained by steam distillation of the flower heads and leaves, for more than 250 years. The oil is complex and varies in composition, as noted above, and depends upon growing conditions, season, soil mineral content, and developmental stage of part collected.5,6
Some of the essential oil components, the chamazulenes and other compounds called proazulenes, have potent anti-inflammatory effects. A correlation between the ploidy level and the ability of Achillea species to synthesize proazulenes has been shown.7
Preitschopf et al found a correlation between the frequency of proazulene-containing yarrows and increased concentrations of available phosphate, magnesium, and manganese in the soil in which the plants are grown.8 The volatile oil of a tetraploid species of Achillea can contain up to 50% chamazulenes.9 Diploid, hexaploid, and octaploid species, however, contain little to no chamazulenes, but can contain alpha-thujone, which has a stimulant effect on uterine musculature and has been used as an emmenagogue in some cultures.4
Other components of the essential oil—menthol and camphor—have bactericidal activity. Salicylic acid has both anti-inflammatory and analgesic activities. Yarrow also contains flavonoids such as rutin and quercetin, which have anti-inflammatory and antispasmodic activity.3 Achilleine, one of the alkaloids found in yarrow, promotes blood coagulation.10 There has been a dearth of studies, however, to substantiate the use of any of these components or their effects in the clinical setting.
Animal Studies
Taran et al evaluated yarrow essential oil vs. a standard concentration of chamazulenes in control oil vs. a neutral control oil in the healing of napalm burns in rabbits. Burns treated with the essential yarrow oil and the standardized chamazulene oil had a significantly faster time to eschar slough compared to control (seven days vs. 24 days, P < 0.001). Subsequent histological studies done on the burn tissue after complete healing revealed that the skin treated with the yarrow essential oil and the standardized chamazulene oil did not differ in appearance from normal skin, whereas the skin of healed control burns had significant distortion of the subdermis and dermis with cytoplasmic and nucleolar vacuolization.11 The authors did not specify, however, the species of yarrow utilized for the study nor was a voucher specimen submitted.
Goldberg et al isolated and studied six constituents of the aqueous extract of yarrow flower heads. The anti-inflammatory activity of each fraction was assessed utilizing the mouse paw edema test.12 Results were compared to known anti-inflammatory agents: corticotrophin, acetylsalicylic acid, dexamethasone, hydrocortisone, and indomethacin. Four of the six fractions produced reductions in inflammation greater than those induced by acetylsalicylic acid.
Clinical Studies
One randomized, placebo-controlled trial from The Netherlands using an herbal mixture of juniper, nettle, and yarrow in a 1:1:1 formulation showed no difference in indices of plaque formation or gingival health in 45 blinded volunteers with moderate gingival inflammation.13 The study did include an in vitro portion in which the antibacterial activity of the pure herbal extract mixture of juniper, nettle, and yarrow against oral bacteria was assessed by the agar dilution method. Despite the fact that some antimicrobial activity was observed, the clinical portion of the study did not show any significant changes from the control rinse in the measured analyses of plaque formation, gum bleeding, or modified gingival index.
Adverse Effects and Contraindications
Yarrow is known to cause allergic contact dermatitis in sensitive individuals. Alpha-peroxyachifolid, the compound isolated from Achillea millefolium blossoms, is responsible for this effect.14,15 The volatile oil of some species contains trace amounts of the chemical thujone, which is an abortifacient, and therefore should not be used by pregnant or lactating women.16 Animal studies have shown achilleine, one of the alkaloids isolated from yarrow, to have in vivo procoagulant activity.10 It should not be used in patients taking anticoagulants.
Conclusion
Yarrow research has a long way to go before the plant can be used with any assurance as a phytomedicine. There is a great deal of variability in constituent content based on ploidy level and environmental conditions. Commercial sources in this country are not well-defined enough to be certain of the genetic identity of the source plant. Even imported yarrow could be any one of a number of species. Therefore, reliable standardized products cannot be manufactured based upon the current level of expertise. At this time, yarrow remains a folk medicine and cannot be recommended for clinical use.
Recommendation
Because of the dearth of any randomized, blinded, controlled clinical studies regarding the use of yarrow and taxonomic classification problems within the species, yarrow cannot be recommended for use, either alone or in combination with other herbs.
Dr. Marcolina is a board-certified internist and geriatrician in Issaquah, WA.
References
1. Castleman M. The Healing Herbs: The Ultimate Guide to the Curative Powers of Nature’s Medicines. Emmaeus, PA: Rodale Press; 1991.
2. Leyel CF. Culpepper’s English Physician and Complete Herbal. North Hollywood, CA: Wilshire Book; 1972.
3. Chandler RF, et al. Ethnobotany and phytochemistry of yarrow, Achillea millefolium, Compositae. Econ Botany 1982;36:203-223.
4. Zeylstra H. Why yarrow? Br J Phytother 1997;4: 184-189.
5. Figueiredo AC, et al. Composition of the essential oils from two populations of Achillea millefolium L ssp millefolium. J Chromatogra Sci 1992;30:392-395.
6. Afsharypour S, et al. Volatile constituents of Achillea millefolium L. ssp. Millefolium from Iran. Flavour Fragrance J 1996;11:265-267.
7. Dastner G, et al. Volatile constituents of Achillea millefolium. Planta Med 1990;56:531.
8. Preitschopf A, et al. Achillea millefolium: Occurrence, ploidal level and preazulene variation. Planta Med 1989;55:596.
9. Haggag MY, et al. Thin layer and gas chromatographic studies on the essential oil from Achillea millefolium. Planta Med 1975;27:361-366.
10. Miller FM, Chow LM. Alkaloids of Achillea millefolium: Isolation and characterization of Achilleine. J Am Chem Soc 1954;76:1353-1354.
11. Taran DD, et al. The wound healing properties of the essential oils of yarrow and Yakut wormwood and khamazulen in napalm burns [in Russian]. Voen Med Zh 1989;8:50-52.
12. Goldberg AS, et al. Isolation of the anti-inflammatory principles from Achillea millefolium (Compositae). J Pharm Sci 1969;58:939-941.
13. Van der Weijden GA, et al. The effect of herbal extracts in an experimental mouthrinse on established plaque and gingivitis. J Clin Periodontol 1998;25: 399-403.
14. Hausen BM, et al. Alpha-peroxyachifolid and other new sensitizing sesquiterpene lactones from yarrow (Achillea millefolium L., Compositae). Contact Dermatitis 1991;24:274-280.
15. Davies MG, Kersey PJ. Contact allergy to yarrow and dandelion. Contact Dermatitis 1986;14:256-257.
16. Farnsworth NR. Potential value of plants as sources of new antifertility agents I. J Pharm Sci 1975;64: 535-598.
August 2001; Volume 4; 91-94
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