Kai Xin San (KXS), a herbal formulation consisting of ginseng (Panax ginseng), hoelen (Wolfiporia cocos), polygala (Polygala tenuifolia) and Acorus gramineus, produces anti-fatigue effects by modulating interleukin-2 (IL-2) and interleukin-4 (IL-4) in a model of chronic fatigue syndrome induced by forced wheel running (Cao et al. 2012). The gene discussed is IL2; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.