Is echinacea effective in treating common cold?
Date of publication of the randomized controlled trial: December 2010
Design
Randomized controlled trial (RCT).
Participants
719 patients (age range: 12 to 80 years, mean age: 33.7 years, male %: 36%) with new-onset common cold.
Intervention
10.2g dried echinacea root during the first 24 hours and 5.1g during each of the next 4 days.
Comparator
Comparison: Echinacea versus placebo.
Major Outcomes
Outcome 1: Area under the curve for global severity, measured by the short version Wisconsin Upper Respiratory Symptom Survey. Higher scores indicated more severe common cold;
Outcome 2: Change in interleukin-8 levels from nasal wash (ng/L);
Outcome 3: Change in neutrophil counts from nasal wash (cells/hpf).
Settings
This trial was performed in an outpatient setting.
Comparison    Echinacea versus placebo
Main Results
Compared to placebo, echinacea do not have significant effect in reducing common cold severity (mean difference (MD): -28, 95% CI: -69.0 to 13.0), interleukin-8 level (MD: 19.0, 95% CI: -75.2 to 72) and neutrophil counts (MD: 1.0, 95% CI: -4.0 to 3.0) among common cold patients.
Comparison: Echinacea versus placebo among common cold patients
Outcome No. of studies (Total number of participants) Mean (SD)/ No. of participants Heterogeneity test (I2) MD (95% CI) Overall quality of evidence*
Intervention Comparator
1 1 (359) 236 (182)/ 183 264 (212)/ 176 Not applicable as there is only 1 study. -28 (-69.0 to 13.0) Low
Outcomes No. of studies (Total number of participants) Median (95% CI)/ No. of participants Heterogeneity test (I2) MD (95% CI) Overall quality of evidence*
Intervention Comparator
2 (ng/L) 1 (338) 58 (18 to 105)/ 170 39 (12 to 106)/ 168 Not applicable as there is only 1 study. 19.0 (-75.2 to 72) Low
3 (cells/hpf) 1 (338) 2 (0 to 5)/ 170 1 (-1 to 4)/ 168 Not applicable as there is only 1 study. 1.0 (-4.0 to 3.0) Low
Keys: SD = standard deviation; MD = mean difference; CI= confidence interval.
Comparison    Echinacea versus placebo
Main Results
Compared to placebo, echinacea do not have significant effect in reducing common cold severity (mean difference (MD): -28, 95% CI: -69.0 to 13.0), interleukin-8 level (MD: 19.0, 95% CI: -75.2 to 72) and neutrophil counts (MD: 1.0, 95% CI: -4.0 to 3.0) among common cold patients.
Comparison: Echinacea versus placebo among common cold patients
Outcome 1
No. of studies (Total number of participants) 1 (359)
Mean (SD)/ No. of participants Intervention 236 (182)/ 183
Comparator 264 (212)/ 176
MD (95% CI) -28 (-69.0 to 13.0)
Overall quality of evidence* Low
Outcomes 2 (ng/L) 3 (cells/hpf)
No. of studies (Total number of participants) 1 (338) 1 (338)
Median (95% CI)/ No. of participants Intervention 58 (18 to 105)/ 170 2 (0 to 5)/ 170
Comparator 39 (12 to 106)/ 168 1 (-1 to 4)/ 168
MD (95% CI) 19.0 (-75.2 to 72) 1.0 (-4.0 to 3.0)
Overall quality of evidence* Low Low
Keys: SD = standard deviation; MD = mean difference; CI= confidence interval.
Conclusion
Benefits
Compared to placebo, Echinacea is not significantly more effective in treating common cold. For Outcome 1-3, the overall quality of evidence is low. Further research is likely to have an important impact on our confidence in this estimate of effect.
Harms
No pattern of adverse effects was observed.
Link to Original Article
https://www.ncbi.nlm.nih.gov/pubmed/21173411
The synopsis is based on the following article:
Barrett B, Brown R, Rakel D, Mundt M, Bone K, Barlow S, et al. Echinacea for treating the common cold: a randomized trial. Annals of Internal Medicine. 2010 Dec 21;153(12):769-77.


* Interpretation of quality assessment results:
• Very low: Further research is most likely to have an important impact on our confidence in this estimate of effect.
• Low: Further research is likely to have an important impact on our confidence in this estimate of effect.
• Moderate: Further research is fairly likely to have an important impact on our confidence in this estimate of effect.
• High: Further research is unlikely to have an important impact on our confidence in this estimate of effect.
• Very high: Further research is most unlikely to have an important impact on our confidence in this estimate of effect.

Details of assessment method can be found at Chung VC, Wu XY, Ziea ET, Ng BF, Wong SY, Wu JC. Assessing internal validity of clinical evidence on effectiveness of CHinese and integrative medicine: Proposed framework for a CHinese and Integrative Medicine Evidence RAting System (CHIMERAS). European Journal of Integrative Medicine. 2015 Aug 31;7(4):332-41.