Bottom Line: Echinacea does not appear to relieve the symptoms of the common cold, but it may shorten the duration of colds when taken within 24 hours of the first cold symptoms.
We do not know exactly how Echinacea works. Echinacea has been studied in the laboratory and with animal subjects. These studies show that different immune cells are stimulated when they are incubated with Echinacea extracts. It is not known whether this same effect occurs in humans. Some compounds found in Echinacea appear to reduce inflammation, relieve pain, and kill bacteria and viruses directly.
To treat the common cold Most clinical trials do not support this use. One clinical trial supports the use of Echinacea for reducing the length of colds, but not the severity of symptoms.
As an antiseptic Laboratory studies suggest that Echinacea has anti-bacterial qualities. This use has not been tested in humans in clinical trials.
To stimulate the immune system Laboratory and animal studies suggest that Echinacea extracts stimulate different parts of the immune system. There is no proof from clinical trials that these effects occur in humans.
To treat viral infections Laboratory studies suggest that Echinacea is anti-viral. This use has not been tested in humans other than to treat the common cold.
For faster wound healing No scientific evidence supports this use.
Common cold: A meta-analysis, which is a complete search of all articles that have been published on a topic, was performed on the effect of echinacea on the common cold. After combining results from available trials, analysts concluded that echinacea did not appear to prevent the onset of the common cold. It was unclear whether echinacea was effective in treating infections because most of the trials examined were designed poorly.
A large scale randomized, placebo-controlled trial was conducted to study the effects of Echinacea angustifolia extracts as prevention and as treatment for common cold. Some subjects were given either the extracts or a placebo before exposing to rhinovirus. Others received treatment on the day of exposure. Treatments would continue for 5 more days and the severity of symptoms and other evidences of immunostimulating activities were measured. The results on 399 volunteers found E.angustifolia is no better than a placebo when used for common cold caused by rhinovirus.
In a clinical trial, echinacea extract or a placebo extract was given to 80 patients twice a day at the first signs of a cold. On average, patients who took echinacea had their cold for a shorter amount of time (six days) compared to patients who took the placebo (nine days), but the groups had equally severe cold symptoms.
In another clinical trial, children aged 2-11 were given echinacea extract or placebo at the first signs of a respiratory tract infection. On average, children who received echinacea did not fare any better than those who only received placebo.
In another clinical trial, 128 subjects received either echinacea juice or placebo three times daily within 24 hours of the onset of cold symptoms. Subjects received treatment until the symptoms were relieved or 14 days had passed. Subjects who received echinacea did not have fewer symptoms or shorter symptom duration than those receiving placebo.
This product is regulated by the FDA as a dietary supplement. Unlike approved drugs, supplements are not required to be manufactured under specific standardized conditions. The product may not contain the labeled amount or may be contaminated. In addition, it may not have been tested for safety or effectiveness.
A group of researchers recently analyzed 59 brands of Echinacea to determine whether their labels were telling the truth. About half of the brands did not contain the quality or species of Echinacea that they claimed on the label, and 10% contained no measurable Echinacea at all.
You are taking immunosuppressants such as tacrolimus or cyclosporine (Echinacea may lessen their effect)
You have an autoimmune disorder such as systemic lupus erythematosus or rheumatoid arthritis, multiple sclerosis, other progressive collagenous disorders, tuberculosis, HIV, or AIDS (Echinacea may aggravate the disorder).
The many Echinacea supplements available in stores contain varying amounts and different species of Echinacea. Therefore, the beneficial results seen with Echinacea in clinical trials may not apply to a product that contains a different species or quality of this herb. One recent study found that about half of the Echinacea brands tested did not contain the type or quality of Echinacea that they claimed on the label, so shop with caution.
Echinacea purpurea belongs to the family Compositae. Extracts of Echinacea derived from the root and aerial parts of the plant are widely used in Europe and USA to treat common cold. Several large scale randomized controlled trials have been conducted to evaluate Echinacea's potential but data are conflicting. Echinacea was shown to stimulate phagocytosis, enhance mobility of leukocytes, stimulate TNF and interleukin 1 secretion from macrophages and lymphocytes, and improve respiratory activity (2)(3) both in vitro and in vivo. The alkylamide, alkaloid, and polyacetylene fractions are thought responsible for such immunomodulatory effects (2). Data from human clinical trials have shown that it is ineffective in preventing common cold caused by rhinoviruses (4) or in treating upper respiratory infections (5)(6). However, conclusions from a meta analysis suggest benefits of Echinacea in reducing the incidence and duration of common cold (7). In addition, results from another trial indicate that if initiated within 24 hours of onset, Echinacea may shorten the duration of colds (8). Echinacea has also been tested in several randomized, placebo-controlled trials for prophylaxis of infections but results are conflicting and more research is required (9)(10).
A major concern for research continues to be the lack of standardization between batches as well as the species and the parts of the plant used. For example, a recent analysis of 59 brand name Echinacea products found that 48% did not contain any Echinacea whereas 10% had no measurable Echinacea. Less than half of the products met the labeled quality standards (1). Commercial products are often mixed with other species including E. angustifolia, and E. pallida.
Several components in echinacea appear to be responsible for its activity. In vitro and in vivo studies suggest echinacea stimulates phagocytosis, enhances mobility of leukocytes, stimulates TNF and interleukin 1 secretion from macrophages and lymphocytes, and improves respiratory activity (2)(3).
A recent analysis of 59 brand name echinacea products found that 48% did not contain the species of Echinacea printed on the label and 10% contained no measurable Echinacea. Less than half of the products met the labeled quality standards (1).
Theoretically, because of potential aggravation of underlying disease state, patients with autoimmune disorders (e.g. systemic lupus erythematosus and rheumatoid arthritis), multiple sclerosis, other progressive collagenous disorders, tuberculosis, HIV, and AIDS should not consume echinacea. (15)
Immunosuppressants: Theoretically echinacea may antagonize the effects of immunosuppressants (15).
CYP3A4: Echinacea inhibits CYP3A4 in vitro, indicating that it could theoretically increase serum levels and adverse effects of drugs like alprazolam, calcium-channel blockers, and protease inhibitors (14).
Melchart D, et al. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev 2001;4:1-15. A complete search of the literature was performed and trials conducted in a randomized fashion were included. Sixteen trials were found in the literature, eight studying efficacy as prophylaxis and eight for the treatment of the common cold and viral infections. Echinacea did not exhibit any pooled effect for the prophylaxis of infections when compared to placebo. Trials studying echinacea for the treatment of infections were poorly designed and pooled effects were not able to be determined. The authors state that the variety of products used and lack of consistent evidence indicate further research is necessary. The reported adverse event rate was similar to placebo.
Schulten B, et al. Efficacy of Echinacea purpurea in patients with a common cold. A placebo-controlled, randomized, double-blind clinical trial. Arzneimittelforschung 2001;51:563-8. A prospective, adequately randomized, placebo-controlled evaluation of echinacea extract given to patients at the first signs of a cold. A total of 80 patients were included in the intent-to-treat analysis. Patients were randomized to receive 5 ml of fresh pressed juice from the aerial parts of Echinacea purpura stabilized in alcohol or placebo twice daily. Primary outcomes measured were severity of symptoms (using the Jackson score) and number of sick days. Seven patients were excluded from the study due to compliance and three patients withdrew, one because of side effects from echinacea. Duration of illness was significantly shorter in the active treatment group, 6 days versus 9 days for placebo (p = 0.0112). Adverse events were similar between treatment groups and consisted primarily of gastrointestinal complaints. The study suggests that echinacea reduces the duration of the common cold, but not necessarily the symptoms associated with it.
Barrett BP, et al. Treatment of the common cold with unrefined echinacea. A randomized, double-blind, placebo-controlled trial. Ann Intern Med 2002;137:939-46. A randomized, double-blind, placebo-controlled trial of 148 college students with recent onset of the common cold. Treatment was by an encapsulated mixture of unrefined echinacea purpurea herb and root and E. angustifolia root taken in 1-g doses six times on the first day and three times on each subsequent day for a maximum of 10 days. Findings showed no significant effect of the echinacea over the placebo. Because the trial tested healthy undergraduate college students, efficacy may be related to general health, age or level of immunocompromization. Furthermore, primary outcome measures were self-reporting of symptoms. Finally, the preparation of echinacea used had not been previously tested for bioavailability or phytochemical constituents. While this study contradicts many studies on the efficacy of echinacea and the common cold, further studies need to be done to account for the factors listed above.
Taylor JA, Weber W, Standish L, Quinn H, Goesling J, McGann M et al. Efficacy and Safety of Echinacea in Treating Upper Respiratory Tract Infections in Children: A Randomized Controlled Trial. JAMA: JAMA 2003;290:2824-30. A randomized, double-blind, placebo-controlled trial of 407 children between two and 11 years-old. Subjects were randomized to receive Echinacea purpurea (3.75 mL or 5 mL twice daily based on age) or placebo at the onset of upper respiratory track infections (URI). Treatment continued until the cessation of symptoms or until ten days had passed. Findings showed no significant effect of echinacea in primary outcome measures of duration and severity of symptoms, number of days of peak severity, number of days of fever or an overall assessment of severity of symptoms by subjects' parents. Children in the treatment group were more likely to develop a rash than children taking placebo. Subjects taking echinacea did have a statistically significant reduction in the number of subsequent URIs, although the value of this finding is unclear.
Yale SH, Liu K. Echinacea purpurea Therapy for the Treatment of the Common Cold. Arch Intern Med. 2004;164:1237-1241. 128 patients participated in this trial of echinacea and upper respiratory tract infections. Patients received either 100 mg of freeze-dried juice of Echinacea purpurea three times a day or placebo. Treatment began within 24 hours of symptom onset and continued until symptoms abated or 14 days had passed. Patients were evaluated by a doctor within 24 hours of starting and completing the trial to verify symptoms. No statistically significant difference was observed between the treatment group and the control for either total symptom score or mean individual symptom score.
Turner R. et al. An Evaluation of Echinacea angustifolia in Experimental Rhinovirus Infections. N Engl J Med. 2005;353(4):341-348. This is a randomized, placebo-controlled trial on 399 healthy volunteers to study the effects of Echinacea angustifolia extracts as prophylaxis and as treatment for common cold. Some subjects were given either Echinacea extracts or a placebo for seven days before exposure to rhinovirus while others received treatment on the day of exposure. Treatments would continue for 5 more days and the severity of symptoms; viral titers and interleukin-8 in nasal-lavage were measured. The results found no statistically significant difference between the groups that used Echinacea and the groups that used a placebo. The authors concluded that the extracts of E.angustifolia have no effects on common cold caused by rhinovirus.
