URIs spread most readily in settings where numerous people are in close contact.
One example of such a setting is the Hajj — an Islamic ceremony that attracts millions of Muslims on a pilgrimage to Mecca. People come from all over the world to congregate in this compact area, and the risk for contagious disease is high. It is estimated that 1 in 3 people experience symptoms of the common cold or flu towards the end of the Hajj celebrations.
Given the context of the Hajj, researchers at the Iran University of Medical Sciences conducted a review of the literature to explore the potential for Echinacea supplements to prevent or treat URIs in at-risk populations.
From a PubMed enquiry using search terms “Echinacea” and “respiratory tract infections,” a total of 66 research articles were included in this review.
Numerous mechanistic studies demonstrated immune-modulating effects of Echinacea. The herb has been shown to boost circulating white blood cells, monocytes and NK cells — effectively enhancing non-specific immunity. In addition, anti-inflammatory effects of Echinacea include enhancement of IL-10 and suppression of TNF-alpha.
Numerous clinical trials and meta-analyses suggest that Echinacea may reduce the severity and duration of symptoms of the common cold. Additional studies suggest that it can effectively prevent URIs. One study showed specific anti-viral activity of Echinacea against the rhinovirus.
Not all studies support the benefits of Echinacea for URIs, however. A Cochrane Review published in 2000 concluded that there was not enough evidence to recommend Echinacea for the prevention of the common cold.
Given the mixed findings of this review, the authors refrain from making any firm recommendations for the use of Echinacea to prevent or treat URIs in at-risk populations. They suggest that Echinacea may offer “mild curative effects” for the common cold and may be most effective when used synergistically in combination products.
