Purple Coneflower (Echinacea Purpurea) Explained Simply

1. What It Is About

Echinacea is the German name for Echinacea, a plant genus. Research focuses mainly on three species: Echinacea angustifolia, Echinacea pallida and Echinacea purpurea. Very different preparations are made from them. An extract is an extract from plant parts, for example from the root or from the herb of the freshly harvested plant. Some extracts are liquids, others are processed into tablets or capsules.

One point is important: the word Echinacea does not refer to a uniform substance, but to a group of extracts from different species and plant parts. An extract from the root is different from one from the herb. The two cannot readily be compared.

Human studies investigate quite different questions. Some test whether a cold can be prevented at all. Others examine whether it runs shorter or milder once it has started. Still others measure laboratory values of the immune system or check whether Echinacea alters the uptake of other medicines.

2. What Studies Show

The question most frequently studied is whether Echinacea prevents colds. A 2019 review pooled several randomised, placebo-controlled trials. Randomised means that chance decides who receives Echinacea and who receives a placebo. In this summary, people who took Echinacea developed an upper-respiratory-tract infection slightly less often than the comparison group 1. The authors themselves note that the included studies were very heterogeneous in design.

The largest single study dates from 2012. 755 healthy people took either an extract from freshly harvested Echinacea or a placebo for four months. The Echinacea group experienced fewer cold episodes, fewer days with a cold and fewer episodes in which painkillers were required. In a subset of colds, a virus could be detected in nasal secretions; there, Echinacea inhibited infections with enveloped viruses. Effects were clearest in people who caught colds repeatedly. Adverse events occurred at similar rates to those under placebo 4.

A 1999 study followed 246 people who already had a cold. A symptom index comprising twelve cold symptoms was measured. Two of the Echinacea preparations tested performed better than placebo; a third did not. All were well tolerated 3.

A smaller 2001 study in 80 adults with early cold symptoms observed a shorter illness duration: six days in the Echinacea group versus nine days in the comparison group 5. Such small studies are indications and often the impetus for larger follow-up trials.

3. What Remains Unclear

Some studies found no difference. A 2002 study in 148 students with an incipient cold tested a mixture of herb and root and found no advantage over placebo on any measured endpoint 2. A study in 48 healthy adults exposed to a cold virus did not reduce the infection rate 6. In 437 volunteers, three different root extracts showed no effect on infection or symptoms 7.

The reason lies in the subject itself: the studies differ in species, plant part, preparation and outcome measure. Consequently, the results cannot be placed cleanly side by side. What needs to be clarified next are trials with uniformly manufactured preparations and identical outcome measures, from which the effect of a single extract can be read reliably.

4. What This Means in Everyday Life

Anyone encountering a preparation can first ask which plant part and which preparation it contains. The word Echinacea alone does not say so. The studies that showed a benefit used specific extracts; the studies without difference used others. Both types of result belong to the same plant.

In one study, adverse events occurred at similar rates to those under placebo 4. A 2015 review, by contrast, found conflicting reports: some studies without serious adverse effects, others with abdominal pain, rash, swelling or dyspnoea 8.

What still needs to be clarified is whether findings from laboratory and cell studies can be transferred to humans and whether a uniformly manufactured preparation yields the same result in several independent studies with identical outcome measures.

All details with study numbers and sources: detailed page on Echinacea (Echinacea purpurea). For children: Echinacea (Echinacea purpurea) for children.