This study evaluated the anti-allergic effect of low molecular weight ${eta}$-glucan (25 kDa) degraded by ${gamma}$-irradiation. Allergy was induced in mouse models administrated with ${gamma}$-irradiated low molecular weight and non-irradiated high molecular weight ${eta}$-glucan, respectively, for 7 days. However, only the mice treated with low molecular weight ${eta}$-glucan had a significantly decreased the total serum IgE and ovalbumin specific-IgE levels, and significantly increased Th 1 cytokine expression compared to only allergy induced mice. The allergic responses could be reduced by low molecular weight ${eta}$-glucan treated ${gamma}$-irradiation through the increased expression of Th 1 response and decreased expression of total IgE and antigen specific IgE.