Hot water extracts of green soybean, Glycine max (WEGS) significantly decreased the levels of ovalbumin (OVA)-specific IgE in mice and significantly suppressed toluene diisocyanate-induced nasal mucosa secretion. An open-label human pilot study including 16 subjects with Japanese cedar pollinosis (JCP) was conducted. The symptom scores for JCP were better in the long-term WEGS intake group than in the short-term intake group. WEGS have great potential as an orally active immune modulator for the treatment of various allergic diseases. We conducted a preliminary investigation of the effects of visible light irradiation on plant extracts, and observed a strong suppressive effect on interleukin (IL)-2 expression in Jurkat cells following treatment with visible light-irradiated ethanol extract from green soybeans (LIEGS). This effect was produced only by extracts from green soybeans and not soybeans of other colors. LIEGS suppressed lipopolysaccharide-induced IL-6, IL-12, and TNF- α expression levels in human monocyte THP-1 cells in a concentration-dependent manner. LIEGS suppressed the development of atopic dermatitis-like skin lesions and reduced the dermatitis scores of NC/Nga mice.