Intervention Review

Echinacea for preventing and treating the common cold

  1. Marlies Karsch-Völk1,*,
  2. Bruce Barrett2,
  3. David Kiefer2,3,
  4. Rudolf Bauer4,
  5. Karin Ardjomand-Woelkart4,
  6. Klaus Linde1

Editorial Group: Cochrane Acute Respiratory Infections Group

Published Online: 20 FEB 2014

Assessed as up-to-date: 5 JUN 2013

DOI: 10.1002/14651858.CD000530.pub3

How to Cite

Karsch-Völk M, Barrett B, Kiefer D, Bauer R, Ardjomand-Woelkart K, Linde K. Echinacea for preventing and treating the common cold. Cochrane Database of Systematic Reviews 2014, Issue 2. Art. No.: CD000530. DOI: 10.1002/14651858.CD000530.pub3.

Author Information

  1. 1

    Technische Universität München/Klinikum rechts der Isar, Institut für Allgemeinmedizin/Institute of General Practice, München, Germany

  2. 2

    University of Wisconsin - Madison, Department of Family Medicine, Madison, Wisconsin, USA

  3. 3

    University of Arizona, Arizona Center for Integrative Medicine, Tucson, Arizona, USA

  4. 4

    Karl-Franzens-University, Institute of Pharmaceutical Sciences, Department of Pharmacognosy, Graz, Austria

*Marlies Karsch-Völk, Institut für Allgemeinmedizin/Institute of General Practice, Technische Universität München/Klinikum rechts der Isar, Orlansstr. 47, München, 81667, Germany. karsch@lrz.tu-muenchen.de.

Publication History

  1. Publication Status: New search for studies and content updated (conclusions changed)
  2. Published Online: 20 FEB 2014

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Abstract

  1. Top of page
  2. Abstract
  3. Plain language summary
  4. Plain language summary

Background

Echinacea plant preparations (family Asteraceae) are widely used in Europe and North America for common colds. Most consumers and physicians are not aware that products available under the term Echinacea differ appreciably in their composition, mainly due to the use of variable plant material, extraction methods and the addition of other components.

Objectives

To assess whether there is evidence that Echinacea preparations are effective and safe compared to placebo in the prevention and treatment of the common cold.

Search methods

We searched CENTRAL 2013, Issue 5, MEDLINE (1946 to May week 5, 2013), EMBASE (1991 to June 2013), CINAHL (1981 to June 2013), AMED (1985 to February 2012), LILACS (1981 to June 2013), Web of Science (1955 to June 2013), CAMBASE (no time limits), the Centre for Complementary Medicine Research (1988 to September 2007), WHO ICTRP and clinicaltrials.gov (last searched 5 June 2013), screened references and asked experts in the field about published and unpublished studies.

Selection criteria

Randomized controlled trials (RCTs) comparing mono-preparations of Echinacea with placebo.

Data collection and analysis

At least two review authors independently assessed eligibility and trial quality and extracted data. The primary efficacy outcome was the number of individuals with at least one cold in prevention trials and the duration of colds in treatment trials. For all included trials the primary safety and acceptability outcome was the number of participants dropping out due to adverse events. We assessed trial quality using the Cochrane 'Risk of bias' tool.

Main results

Twenty-four double-blind trials with 4631 participants including a total of 33 comparisons of Echinacea preparations and placebo met the inclusion criteria. A variety of different Echinacea preparations based on different species and parts of plant were used. Evidence from seven trials was available for preparations based on the aerial parts of Echinacea purpurea.

Ten trials were considered to have a low risk of bias, six to have an unclear risk of bias and eight to have a high risk of bias. Ten trials with 13 comparisons investigated prevention and 15 trials with 20 comparisons investigated treatment of colds (one trial addressed both prevention and treatment).

Due to the strong clinical heterogeneity of the studies we refrained from pooling for the main analysis. None of the 12 prevention comparisons reporting the number of patients with at least one cold episode found a statistically significant difference. However a post hoc pooling of their results, suggests a relative risk reduction of 10% to 20%. Of the seven treatment trials reporting data on the duration of colds, only one showed a significant effect of Echinacea over placebo. The number of patients dropping out or reporting adverse effects did not differ significantly between treatment and control groups in prevention and treatment trials. However, in prevention trials there was a trend towards a larger number of patients dropping out due to adverse events in the treatment groups.

Authors' conclusions

Echinacea products have not here been shown to provide benefits for treating colds, although, it is possible there is a weak benefit from some Echinacea products: the results of individual prophylaxis trials consistently show positive (if non-significant) trends, although potential effects are of questionable clinical relevance.

 

Plain language summary

  1. Top of page
  2. Abstract
  3. Plain language summary
  4. Plain language summary

Echinacea for preventing and treating the common cold

Preparations of the plant Echinacea are widely used in some European countries and in North America for common colds. Echinacea preparations available on the market differ greatly as different types (species) and parts (herb, root or both) of the plant are used, different manufacturing methods (drying, alcoholic extraction or pressing out the juice from fresh plants) are used and sometimes also other herbs are added.

We reviewed 24 controlled clinical trials with 4631 participants investigating the effectiveness of several different Echinacea preparations for preventing and treating common colds or induced rhinovirus infections. Our review shows that a variety of products prepared from different Echinacea species, different plant parts and in a different form have been compared to placebo in randomized trials. Due to the significant differences in the preparations tested, it was difficult to draw strong conclusions. Five trials were rated as having a low risk of bias in all five categories of the Cochrane 'Risk of bias' tool. Five more trials were rated as low risk of bias, having an unclear risk of bias in only one category. Eight trials were rated as having a high risk of bias in at least one category and the remaining six as having an unclear risk of bias.

The majority of trials investigated whether taking Echinacea preparations after the onset of cold symptoms shortens the duration, compared with placebo. Although it seems possible that some Echinacea products are more effective than a placebo for treating colds, the overall evidence for clinically relevant treatment effects is weak. In general, trials investigating Echinacea for preventing colds did not show statistically significant reductions in illness occurrence. However, nearly all prevention trials pointed in the direction of small preventive effects. The number of patients dropping out or reporting adverse effects did not differ significantly between treatment and control groups in prevention and treatment trials. However, in prevention trials there was a trend towards a larger number of patients dropping out due to adverse events in the treatment groups.

The evidence is current to July 2013.

 

Plain language summary

  1. Top of page
  2. Abstract
  3. Plain language summary
  4. Plain language summary

Ehinaceja za sprječavanje i liječenje prehlade

Ehinaceja za sprječavanje i liječenje prehlade

Pripravci koji se temelje na biljki ehinaceji naveliko se koriste za prehladu u nekim europskim zemljama i u Sjevernoj Americi za liječenje prehlade. Na tržištu se može naći velik broj pripravaka na bazi ehinaceje, ali ti se pripravci znatno razlikuju po tipu (vrsti), dijelovima biljke (stabljika, korijen ili oboje) i metodama proizvodnje (sušenje, alkoholna ekstrakcija ili prešanje soka iz svježih biljaka), a ponekad su pripravcima dodane i druge biljke.

Cochrane sustavni pregled analizirao je 24 kontrolirane kliničke studije s ukupno 4631 ispitanika u kojima je istražena učinkovitost nekoliko različitih pripravaka ehinaceje za sprječavanje i liječenje prehlade il infekcija rhinovirusima. Sustavni pregled literature pokazuje da je niz proizvoda koji se temelje na različitim vrstama ehinaceje, različitim dijelovima te biljke i u različitom obliku u pokusima uspoređeno s placebom. Zbog velikih razlika u pripravcima koji su korišteni u istraživanjima nije moguće donijeti čvrste zaključke. Kvaliteta studija značajno se razlikovala – samo je 5 studija ocijenjeno kao visokokvalitetno. Većina studija istraživala je da li uzimanje pripravaka ehinaceje nakon početka prehlade skraćuje trajanje bolesti ili ublažava simptome, u usporedbi s placebom.

Iako se može činiti moguće da su neki proizvodi ehinaceje učinkovitiji nego placebo u liječenju prehlade, ukupni dokazi za klinički važan učinak liječenja prehlade ehinacejom su slabi. Istraživanja u kojima je proučavano može li ehinaceja smanjiti prehlade nisu pokazala statistički značajno smanjenje pojave bolesti. U studijama je bilo naznaka malog preventivnog učinka. Broj ispitanika koji je odustao od istraživanja nije se razlikovao između eksperimentalnih i pokusnih skupina u prevencijskim i terapijskim studijama. Međutim, u studijama koje su istraživale preventivni učinak ehinaceje uočen je veći broj ispitanika koji su odustajali od istraživanja zbog nuspojava u skupini koja je uzimala ehinaceju.

Dokazi se temelje na literaturi objavljenoj do srpnja 2013.

Translation notes

Translated by: Croatian Branch of the Italian Cochrane Centre