The modern data supporting echinacea, the Indigenous American botanical
Perhaps you know it for its distinct flower – a pronounced brown central cone, surrounded by delicate purple petals – and its common botanical name, purple coneflower. Or maybe, you know it as a natural remedy to take for protection against the sniffles and sneezes of cold and flu season. As a common North American wildflower, Echinacea purpurea undoubtedly has crossed your path at some point, be it on a summer stroll through the prairies of the Midwest, or as a tea or tincture you took when feeling a tingle in the throat or heaviness in your lungs.
Echinacea spp. is one of the earliest botanicals that North American European settlers learned of from the indigenous inhabitants of the region who made use of its aerial parts for ailments ranging from toothache to snakebites to gastrointestinal distress to rheumatism.[1] Research in the early 1900s pointed toward the use of echinacea for pyogenic infections, including treatment of tuberculosis and infections attributed to Staphylococcus and Streptococcus spp.[2]
Fast-forward to 2020, and a world more aware of infectious disease than the majority of us have ever been in our lifetime. In addition to considering the importance of essential vitamins and minerals and how they may impact immune function and infection resistance,[3] certain botanicals such as echinacea also have had increased use simply for what we know them for: prevention of the common, cold-related sniffles and sneezes. In this article, we take a look at the science backing echinacea for our modern problems, in particular, those related to immune system function and respiratory tract infections.
The Many Forms of Echinacea
In addition to Echinacea purpurea, E. pallida and E. angustifolia are commonly used medicinally.[4] Preparations can be found that use all the aerial parts (found above the ground), just the flowers, only the roots, or a combination of these fractions. Common techniques used to extract the bioactive constituents of echinacea include pressing the fresh aerial parts or flowers for their juice, which is subsequently dried for inclusion in tablets or capsules, or the use of alcohol to extract a greater portion of the lipophilic substances.
Many compounds found in echinacea contribute to its medicinal activity.[5] Alcohol extractions typically contain higher levels of the lipophilic alkylamides and polyacetylenes while the pressed juices or water extracts contain more arabinogalactans and polysaccharides.[4],[6] Although some prefer a traditional alcohol extraction, others have preference for the fresh-pressed juice. Both have been demonstrated to have antiviral activity.[7]
Echinacea and the Immune System
As early as 1915, studies demonstrated that the power of echinacea perhaps stemmed from its ability to stimulate immune system function.[1] Observations at that time suggested echinacea increased the phagocytic power of leukocytes.[8] Modern research reinforces these findings, with cell studies showing that echinacea stimulates macrophage production of cytokines and nitric oxide, a typical defensive response to an infectious trigger, also promoting T cell proliferation and enhancing T cell activity.[9],[10],[11],[12] In animals and humans, echinacea preparations have also been shown to increase white blood cell counts.[13],[14] In one such double-blind, placebo-controlled study, 500 mg daily of a dried, fresh-pressed extract of E. purpurea flowers was shown to significantly improve scores of immunological vigor as well as increase lymphocytes and CD4+ T cell counts compared to placebo.[15]
Although at one time echinacea was ubiquitously referred to as an immunostimulant, we now increasingly find it described as having immunomodulatory activity.[16] In addition to the immunostimulatory activity described here and elsewhere,4 preparations of echinacea have been observed to have anti-inflammatory and antioxidant effects as well.[5],[17] In response to rhinovirus-induced inflammation, cell studies have also shown that a preparation of E. purpurea aerial parts inhibited virus-induced pro-inflammatory cytokine secretion.[18] Further research in human subject suggests echinacea attenuates the potentially damaging oxidative aspect of the immune response.[19]
A preparation of the fresh pressed juice of the aerial parts of E. purpurea has been shown, in animals, to help protect against stress-induced immunosuppression.[20] However, it also attenuated the stress-related increase in pro-inflammatory cytokines, showing how echinacea can have a balancing or normalizing effect on immune function. Human studies have shown similar results, discussed at length herein. In animals, echinacea has been shown to enhance overall longevity,[21] also increasing survival of immunosuppressed animals in settings of typically lethal bacterial and fungal infections.[22]
Echinacea and the Common Cold
We see much of the clinical research surrounding echinacea focused on its effects in prevention and/or treatment of the common cold. Although larger Cochrane reviews have not shown conclusive benefits,[23],[24] methodology, product quality, and study size each may play a role. In a 2006 Cochrane review of echinacea for the treatment or prevention of colds, a significant effect for treatment of cold was seen in nine studies, with a trend seen in one, and no effect seen in six.[23]Two large meta-analysis also found supplementation with echinacea to be of benefit, showing that the likelihood of experiencing cold symptoms was 55% to 58% higher in individuals not taking echinacea and that cold duration was an average of 1.4 days shorter in those taking echinacea.[25]When looking only at colds due to clinical inoculation (as opposed to spontaneous occurrence, which may be confounded by many factors) the likelihood of experiencing a cold was 55% higher with placebo than echinacea treatment.[26]
In a four-month randomized, double-blind, placebo-controlled trial of 755 healthy adults, daily supplementation of echinacea was found to reduce the total number of cold episodes, number of “episode” days, and use of painkillers for treatment of cold symptoms.[27] Echinacea was taken three times daily for the purpose of prevention, and participants were instructed to increase dosing to five times a day with acute symptoms. Noteworthy was the effect echinacea had on recurrent infections, and the study found the preventative effects increased with treatment compliance based on assessment of unused product and treatment diaries. Sampling of nasal secretions with the occurrence of acute cold symptoms found that echinacea was particularly effective for colds due to enveloped viral infections. This study is of particular interest because echinacea is typically seen as a botanical for acute use – but clearly, it has benefits for prevention when taken regularly for longer periods.
Clinical studies also reflect the effectiveness of echinacea with typical acute use, with high, frequent dosing at the onset of an infection and continued for a short duration thereafter. In one such study, participants were instructed to take echinacea eight times daily on the first day they experienced cold symptoms, and three times daily the six following days.[19] With this protocol, echinacea was shown to decrease total daily symptom scores compared to placebo on all days after day one. Levels of neutrophils were higher in those receiving echinacea than placebo when assessed on days 3 and 8, and at day 8 remained significantly higher than baseline only in the echinacea group. However, the neutrophil oxidative burst capacity, associated with free radical generation, was significantly lower in the group receiving echinacea than placebo at day 8, and although not significant, the echinacea group had a greater increase in erythrocyte superoxide dismutase activity, suggesting enhanced free radical scavenging.
Echinacea and Recurrent Respiratory Infections
A 2015 meta-analysis of randomized controlled trials (RCTs) considered the impact of echinacea on recurrent respiratory tract infections and their complications.[28] Six RTCs (including 2458 individuals) were found that had the methodological quality level necessary for consideration in the analysis; of these, three considered an ethanol extract, two the pressed juice, and one, a glycerol extract. Use of echinacea was shown to reduce the risk of recurrent respiratory infections, with an even greater effect seen in two of the studies in individuals considered to have a higher susceptibility, stress level, or immunological weakness.[27],[29] Complications of pneumonia, otitis media, and tonsillitis/pharyngitis were also approximately halved with echinacea treatment. Of these, the greatest decrease was seen in pneumonia, with the incidence being approximately 65% less in those treated with echinacea.
Echinacea and Pediatrics
Echinacea also has been studied in multiple clinical trials focused on a pediatric population, including children as young as one year of age. In one randomized, double-blind, placebo-controlled trial of children over the fall/winter period, it was found that, compared to placebo, treatment with echinacea during upper respiratory infections (URIs) significantly reduced the risk of developing a subsequent URI by 28%.[30] Echinacea was not shown to reduce URI duration or severity when taken for treatment of URIs, although the children taking echinacea had significantly less URIs compared to the placebo group over the four month observational period.[31]
Another study in children one to five years of age assessed the effectivity of a combination of echinacea, propolis, and vitamin C, administered daily for 12 weeks. It was found that this combination significantly reduced the number of illness episodes and days with fever compared to placebo.[32] Another study of echinacea as a monotherapy in children had methodological errors, thus the impact of echinacea on recovery from a URI could not be accurately assessed.[33]
Safety of Echinacea
A 2016 review of the safety data of oral echinacea preparations concludes “Altogether, the different evaluated Echinacea preparations are well-tolerated herbal medicines in the management in children and adults alike,” however, does note that caution should be exercised in children with atopy and asthma.[34] In a few placebo-controlled studies surveyed in this review the rates of reporting of mild gastrointestinal symptoms, headache or dizziness, or fatigue was higher in the groups receiving echinacea, but not dramatically so. In one study of children, it was observed that a greater percentage of the 200 children receiving echinacea developed a rash (7%, compared to 2.7% in the placebo group), and there were two occurrences of respiratory stridor leading to the withdrawal of these children from the study.31 However,in other large studies of pediatric populations, echinacea was well tolerated.32,33,[35]
In a small study of atopic individuals, it was found that 19% had reactivity to echinacea with skin allergy testing.[36] However, a large, multicenter, two year observational study of 18,830 patients using botanical medicine that contained herbs from the Asteraceae family (which includes echinacea, chamomile, and calendula) found that there were no serious adverse events involving the use of these common botanicals.[37] Eleven non-serious adverse events were reported in a subgroup of 6961 people.
Pregnancy is another setting in which safety data must be uniquely considered. For this there is data from a study of women who were followed after reporting prior use of echinacea during their pregnancy. One-hundred twelve of the 206 women included used echinacea during the first trimester of their pregnancy and the dosage ranged from 250 to 1000 mg/day (of dried herb preparations) for a period of 5 to 7 days.[38] The pregnancy outcomes of the echinacea-using population were compared to those of 206 women who did not use echinacea during their pregnancies, finding that there was no statistical differences between the groups. Preclinical data also does not suggest negative reproductive or developmental effects;34 however, these collective findings are not adequate to make the conclusion that echinacea can be safely used during pregnancy without further controlled, well-designed studies. There also is not adequate evidence to conclude its safety in lactation.[39]
Although many think of echinacea as a therapy for acute or short-term use, there are studies in which it has been used for longer periods, even in children.32 No abnormalities have been seen with daily supplementation up to four months’ time, aside from an aversion to its taste.[27],[34]
Seeking a quality echinacea product is paramount, as a 2003 study well elucidates. Of 59 echinacea products surveyed, purchased from retail outlets in Denver, CO, it was found that 10% had no measurable echinacea content, 48% incorrectly identified the species present, and even 57% of the 21 standardized preparations did not contain that which was stated.[40]
Available studies suggest echinacea enhances the immune response in a balanced fashion, offering protection for adults and children alike from the everyday sniffles and sneezes of cold and flu season. As we seek to minimize sick days from work and school due to these common seasonal issues, echinacea may be one to keep handy in the back pocket.
Dr. Carrie Decker graduated with honors from the National College of Natural Medicine (now the National University of Natural Medicine) in Portland, Oregon. Prior to becoming a naturopathic physician, Dr. Decker was an engineer, and obtained graduate degrees in biomedical and mechanical engineering from the University of Wisconsin-Madison and University of Illinois at Urbana-Champaign respectively. Dr. Decker continues to enjoy academic research and writing and uses these skills to support integrative medicine education as a writer and contributor to various resources. Dr. Decker supports Allergy Research Group as a member of their education and product development team.
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