Volume 37, Issue 4, Page 22 (April 2006)

LESLIE S. BAUMANN, M.D.

DR. BAUMANN is director of cosmetic dermatology at the University of Miami. To respond to this column, or to suggest topics for future columns, write to Dr. Baumann at our editorial offices via e-mail at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Echinacea belongs to the Asteraceae (formerly Compositae) family and was traditionally used by Native Americans for sundry indications beginning, according to the earliest archeological evidence, in the 1700s.

The conditions for which various tribes used this herb included the common cold, bronchitis, upper respiratory infections, coughs, wounds, burns, insect bites, toothaches, inflammatory illnesses, stomach cramps, and snake bites. E. purpurea, E. angustifolia, and E. pallida were and remain the three species of Echinacea found to be most effective for medical purposes (Forsch. Komplementarmed. Klass. Naturheilkd. 2003;10:9–12; Wien. Med. Wochenschr. 1999;149:185–9; Biochem. Pharmacol. 2000;60:155–8).

Rheumatism, neuralgia, and rattlesnake bites were the indications for the first commercial preparation of echinacea: Meyers Blood Purifier, which appeared on the market in the United States around 1880.

By 1900, echinacea was the country's most frequently used botanically derived medical formulation, and it remained popular until the advent of antibiotics in the middle of the 20th century (Forsch. Komplementarmed. Klass. Naturheilkd. 2003;10:9–12).

Today, echinacea is extremely popular again for its perceived benefits in lessening the intensity of—and maybe even warding off—the common cold.

Although this botanical compound inspires widespread public confidence, the medical community has maintained a healthy dose of skepticism regarding its potential effectiveness and highly touted immunomodulatory properties.

A recent study on the effects of E. angustifolia root extracts on rhinovirus infection suggests that this stance may be well founded.

In the study, 437 volunteers (of whom 399 were used for data analysis) were randomized to receive prophylaxis 7 days prior to a virus challenge or treatment at the time of the challenge with one of three distinct echinacea preparations derived from E. angustifolia or placebo.

No statistically significant effects were seen on infection rates or cold symptom severity in the groups receiving echinacea. The authors were careful to point out, though, that these lackluster results are not generalizable to other echinacea formulations or other doses, and that the extracts studied—alone or in combination—did not confer clinically significant benefits against rhinovirus infection (N. Engl. J. Med. 2005;353:341–8).

In fact, these findings would not appear to apply to a German study of the Echinacea species known as the purple coneflower, E. purpurea. This species is the most frequently used herbal agent in Germany for immunomodulation. Formulations of the herb made from pressed juice of the flowering aerial parts of the plant have been shown to significantly reduce the severity and length of common colds in adults and children. It is thought that stimulation of macrophages and induction of cytokines are integral to the mechanism of action, with glycoproteins, polysaccharides, and alkamides serving as the major active components (Wien. Med. Wochenschr. 2002;152:407–11).

E. purpurea formulations have been shown by investigators to be safe and well tolerated (Wien. Med. Wochenschr. 1999;149:185–9). Much of the research on this native American herb has been conducted in Germany, where commercial cultivation began around 1939 (Forsch. Komplementarmed. Klass. Naturheilkd. 2003;10:9–12).

One of the earliest studies of the effects of echinacea on the skin was conducted 20 years ago using E. angustifolia. An extract of the roots displayed sufficient anti-inflammatory activity to warrant inclusion in cosmetic formulations.

The topically applied raw extract was shown to dose-dependently inhibit edema induced by the application of various irritants to mice and rats. The extract was stronger than the positive control, the topical nonsteroidal anti-inflammatory agent benzidamine (Food Chem. Toxicol. 1985;23:317–9).

Antioxidant Properties

In a study completed a decade ago, several characteristic constituents of echinacea were qualitatively and quantitatively assessed and shown to protect against the free-radical-induced degradation of type III collagen.

After exposure to superoxide anion and hydroxyl radicals generated by the xanthine/xanthine oxidase/Fe2+/EDTA system, collagen degradation was dose-dependently inhibited by all of the compounds tested, including—in descending order of potency—echinacoside, chicoric acid, cynarine, caffeic acid, and chlorogenic acid.

The investigators concluded that these typical echinacea constituents effectively protected collagen from free-radical damage by scavenging reactive oxygen species and/or C-, N-, and S-centered secondary radicals. Significantly, they suggested that the topical application of echinacea extracts has the potential to prevent or treat UV-induced photodamage (Planta Med. 1995;61:510–4).

Another study that was done 5 years later demonstrated that methanol extracts of freeze-dried E. angustifolia, E. pallida, and E. purpurea roots had the capacity to scavenge hydroxyl radicals, 1,1-diphenyl-2-picrylhydrazyl radicals, and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals.

The prolonging of the lag phase of the peroxidation of soybean liposomes as well as the suppression of the oxidation of human low-density lipoprotein was ascribed to the apparent antioxidant activity and transition-metal chelating of these botanical extracts (J. Agric. Food Chem. 2000;48:1466–72).

In an analysis of the chemical constituents of the roots and leaves of E. purpurea, E. angustifolia, and E. pallida, investigators found that all these species had caffeoyl conjugates and alkamides in common, but with numerous differences.

The primary active ingredients were chicoric acid and verbascoside in E. purpurea extracts; cynarine and dodeca-2E,4E,8Z,10Z/E-tetraenoic acid isobutylamide in E. angustifolia; and echinacoside and 6-O-caffeoylechinacoside in E. pallida. Nevertheless, the extracts of all three species exhibited antioxidant activity in free-radical scavenging and lipid peroxidation assays (J. Pharm. Pharmacol. 2001;53:849–57).

Differentiation of the components is important because the three species are not easy to discern, and have likely been used for similar indications but with varying effects caused by differences in composition, according to a follow-up study by other researchers. In that study, it was found that echinacoside—the caffeoyl derivative prevalent in E. pallida and found only in trace amounts in E. angustifolia—conferred anti-inflammatory and wound-healing properties after topical application on rats, which investigators attributed to echinacoside's antihyaluronidase activity (J. Ethnopharmacol. 2002;79:265–72).

In addition, a more recent study has demonstrated that the phenolic concentrations in various commercial echinacea medicines vary.

This study, which was designed to quantify caffeic acid concentrations in echinacea, revealed that the roots and derivatives of E. angustifolia, E. pallida, and E. purpurea are good sources of natural antioxidants, with the concomitant potential to impart protective benefits (J. Pharm. Biomed. Anal. 2004;35:289–301).

Another recent investigation demonstrated that alkamides derived from the roots of three different Echinacea species exhibited anti-inflammatory activity (J. Nat. Prod. 2005;68:773–6).

Therapeutic Uses

Key aspects of the chemistry and activity of echinacea remain poorly understood, such as its mechanism of action, bioavailability, and relative potency (Biochem Pharmacol. 2000;60:155–8).

The prevailing wisdom—perhaps suffering a blow from the recent New England Journal of Medicine study—suggests that this herb is best used as a treatment rather than as a preventive agent. Most investigators researching various Echinacea species have determined that some preparations successfully alleviate symptom severity and duration (Biochem Pharmacol. 2000;60:155–8).

The results of research suggest a range of applications for this botanical group. A study conducted 3 years ago showed that eight taxa of the genus Echinacea exhibited in vitro antiviral activity against herpes simplex virus (HSV) type 1 upon visible and UVA light exposure. E. pallida and E. purpurea were the most potent, and root extracts containing alkenes and amides were most active overall (Planta Med. 2002;68:780–3).

E. purpurea also has been recommended as a tool in the armamentarium for treating psoriasis as well as alleviating the inflammation characteristic of several cutaneous conditions (Clin. Dermatol. 2001;19:474–7). In a topical formulation, echinacea has been shown to be effective in treating eczema, first-degree burns, and HSV (Dermatol. Ther. 2003;16:106–13).

Although potentially protecting the skin from photodamage, researchers have also found that echinacea possesses phototoxic attributes against certain fungi.

Researchers have shown that hexane extracts of Echinacea slowed the growth of several yeast strains under near-UV exposure and—less potently—without irradiation, suggesting conventional antifungal activity as well. The yeast strains studied were Saccharomyces cerevisiae, Candida shehata, C. kefyr, C. albicans, C. steatulytica, and C. tropicalis.

Ketoalkenes and ketoalkynes, which are pervasive in Echinacea roots, are believed to be responsible for this phototoxic antifungal property (Planta Med. 2000;66:241–4).

It remains to be seen what effect, if any, the negative publicity regarding the recent trial reported in the New England Journal of Medicine will have on the popularity of echinacea.

This botanical has been used for medical purposes for more than 300 years and boasts a deep base of supporters. The evidence of efficacy for dermatologic indications, albeit relatively sparse, warrants further research.

Although echinacea is well respected by the medical community in Germany and is approved by its Commission E, much more research and more extensive, randomized, controlled trials are needed for the popular botanical to attain wider medical acceptance in the United States and, perhaps, to enter the recognized dermatologic armamentarium.

PII: S0037-6337(06)71167-6

doi:10.1016/S0037-6337(06)71167-6

© 2006 Elsevier Inc. All rights reserved.