Echinacea purpurea stimulates the immune response and is promotedto reduce symptom severity and the duration of upper respiratorytract infections. The researchers sought to determine the efficacyof a standardized preparation of Epurpurea in reducing symptomseverity and duration of the common cold.
A randomized, double-blind, placebo-controlled design was used.Patients received either 100 mg of E purpurea (freeze-driedpressed juice from the aerial portion of the plant) or a lactoseplacebo 3 times daily until cold symptoms were relieved or untilthe end of 14 days, whichever came first. Symptoms (sneezing,nasal discharge, nasal congestion, headache, sore or scratchythroat, hoarseness, muscle aches, and cough) were scored subjectivelyby the patient and recorded daily in a diary. Kaplan-Meier curveswere used to estimate the survival function of time to resolutionin each group. The Wilcoxon rank-sum test was used to comparetime to resolution between the 2 groups.
One hundred twenty-eight patients were enrolled within 24 hoursof cold-symptom onset. Group demographic distribution was comparablefor gender, age, time from symptom onset to enrollment in thestudy, average number of colds per year, and smoking history.No statistically significant difference was observed betweentreatment groups for either total symptom scores (P = .29.90)or mean individual symptom scores (P = .09.93). The timeto resolution of symptoms was not statistically different (P= .73).
It is probably not a surprise that inconsistent results havebeen found in different studies, because there is no requiredstandardization for potency or content of echinacea. We canthank the US Congress, who in the mid-1990s capitulated to thefood-supplements industry and removed Food and Drug Administrationregulation of echinacea and other similar products. Althoughwe generally think of echinacea as fairly harmless, it can reducethe effectiveness of corticosteroids, which would be commonlyused in viral-induced asthma. It also can cause hypersensitivityreactions to persons allergic to ragweed.