The weather here in Liverpool is getting progressively colder and our bodies have to work harder to keep warm, leaving us more susceptible to infection. If you suffer from repeated colds at this time of year, some herbal help may be what you need to boost you immune system. There are many herbs that are used to prevent colds which act as immune stimulants and research has suggested a wide range of mechanisms for their action.

Echinacea species is probably the best known herb used to prevent and treat colds and flu. Human studies have had mixed results, however, this may be due to differences in doses and preparations. A recent review concluded Echinacea effective in preventing cold symptoms (Schoop et al., 2006). Considerable evidence of immune-stimulating properties includes a clinical trial showing increase in innate immune response through increase in white blood cells, including Natural Killer cells which particularly target cold viruses (Goel et  al., 2005). Other studies suggest activation of a part of the immune system consisting of a variety of protein molecules, called complement (Alban et al., 2002) and stimulation of lymphocytes which respond to specific viruses (Zhai et al., 2007).

Astragalus membranaceus (milk vetch) is commonly used to boost the immune system and prevent colds. There is a large body of evidence spanning decades concerning a variety of immune system effects. Most research has not been on humans however, in a small clinical trial, Astragalus demonstrated lymphocyte activation (Brush et al., 2006) and in another small human trial, it was associated with activation and proliferation of immune cells (particularly CD8 and CD4-T cells). Use of Astragalus is however generally avoided in acute infection.

Panax ginseng is most commonly used to enhance the body’s response to stress but also has beneficial effects on the immune system; it has been suggested that this may be via Natural Killer cell activity (Kim et al., 1990). As with Astragalus, Panax ginseng is avoided in acute infection.

How a herbalist might approach cold prevention

Stimulating the immune system is just one aspect of treatment in cold prevention. A herbalist will treat the individual by addressing any ways in which he or she is susceptible to being infected. This may include problems with mucous membranes of the upper respiratory tract, how the body responds to stress and problems with elimination of waste metabolites. Optimum diet and lifestyle will also be addressed. Generally, the better the overall health of the individual, the less likely they will be to become infected with cold viruses and if they do, they will deal with it more effectively.


Alban S, Classen B, Brunner G, Blaschek W. (2002) ‘Differentiation between the complement modulating effects of an arabinogalactan-protein from Echinacea purpurea and heparin’ Planta Med. 68(12):1118-24.

Brush J, Mendenhall E, Guggenheim A, Chan T, Connelly E, Soumyanath A, Buresh R, Barrett R, Zwickey H. (2006) ‘The effect of Echinacea purpurea, Astragalus membranaceus and Glycyrrhiza glabra on CD69 expression and immune cell activation in humans’, Phytother Res 20:687-695.

Goel V, Lovlin R, Chang C, Slama JV, Barton R, Gahler R, Bauer R, Goonewardene L, Basu TK. (2005) ‘A proprietary extract from the echinacea plant (Echinacea purpurea) enhances systemic immune response during a common cold’, Phytother Res. 19(8):689-94.

Kim JY ‌, Germolec DR‌ and Luster MI (1990)‌ ‘Panax Ginseng as a Potential Immunomodulator: Studies in Mice’ Immunopharmacology and Immunotoxicology 12(2):257-276

Schoop R, Klein P, Suter A, Johnston SL. (2006) ‘Echinacea in the prevention of induced rhinovirus colds: a meta-analysis.‘ Clin Ther. 28(2):174-83.

Zhai Z, Liu Y, Wu L, Senchina DS, Wurtele ES, Murphy PA, Kohut ML, Cunnick JE. (2007) ‘Enhancement of innate and adaptive immune functions by multiple Echinacea species’ J Med Food 10(3):423-34.