Echinacea may help to slightly reduce the risk of getting an upper respiratory tract infection, but does not decrease length of illness

David S, Cunningham R. L'échinacée pour la prévention et le traitement des infections des voies respiratoires supérieures: une revue systématique et méta-analyse Complement Ther Med. 2019;44:18-26.

Review question

Are echinacea products safe and effective for the prevention and treatment of upper respiratory tract infections (URTIs)?

Background

URTIs are a set of common conditions that involve infections of the nose, sinuses, pharynx or larynx. Globally, over 17 billion URTIs occurred in 2015. Echinacea is an incredibly popular supplement used to help prevent and treat URTIs. However, past systematic reviews and meta-analyses found mixed results on the effectiveness and safety of echinacea, furthering the debate around its use. There is now more research on echinacea available, prompting the need for a new systematic review of where the evidence currently stands.

How the review was done

This is a systematic review of 29 randomized controlled trials (RCTs). These studies were published between 1996 and 2016. Sixteen of the RCTs were included in a meta-analysis. Key features of the included studies were:

• Most participants were 18 years old and over, but a few studies included or focused on those between 1-12 years of age. 
• Participants used an echinacea product (e.g., capsules, juice, etc.) that contained one or two species of echinacea (e.g., E. purpurea, E. angustifolia, E. pallidae). In most studies, participants were exposed to a URTI causing virus naturally, while some were exposed to one purposefully through a specific vaccination.
• Researchers counted the number of people with at least one URTI, how long the URTI lasted, and the number of people who had at least one negative side effect.
• Researcher compared people who used echinacea to people in a control group receiving a placebo—such as vegetable oil, beeswax, herb powder, lactose, chocolate flavoured syrup, etc.).  

What the researchers found

Overall, compared to placebo, echinacea products:

• reduced the likelihood of experiencing at least one URTI by between 12 to 22%;
• had no effect on the length of the URTI; and
• showed no difference in the number of participants experiencing at least one adverse event with short-term use, suggesting echinacea is safe.

The studies included in the review were conducted very differently, making it difficult to know the type of echinacea product and dose that may be beneficial.

Conclusion

Echinacea may reduce the risk of getting a URTI by a small amount with no increased risk of negative side effects in the short-term, but it does not seem to reduce the duration of a URTI. Real-world effectiveness is also questionable, and more long-term high-quality research is needed.