Mucosal damage is commonly observed in food-sensitive enteropathy in infants, and the generation of leukotrienes is involved in the pathogenesis of this enteropathy. Because supplementingn-3 fatty acids is known to modify the production of leukotrienes, we investigated whether a change of dietary fatty acid composition affects leukotriene synthesis and food hypersensitivity reactions in the intestine by using a mouse model of food-sensitive enteropathy. The model was prepared by feeding ovalbumin to BALB/c mice after intraperitoneal injection of cyclophosphamide. Diets were prepared from soybean oil (control), perilla oil, lard, corn oil, and 0.125 volume of corn oil (low fat diet) and given to mice for 4 wk. Villous heights, crypt depths, leukotriene B4and C4production in the intestine were measured. Crypt hyperplasia and villous atrophy were severer in the corn oil-fed group than those of control group, whereas mucosal damage in the perilla oil and low fat diet groups was minimal. In the corn oil-fed group, red blood cell membrane levels ofn-3 fatty acids were lower than the control, and the synthesis of leukotrienes was highest among all groups. In the perilla oil and low fat diet groups,n-6 fatty acids were lower than those of control group and leukotriene production was significantly suppressed. These results indicate that reducing cell membrane levels ofn-6 fatty acids by feeding lessn-6 fatty acids or supplementingn-3 fatty acids, is important to suppress leukotriene biosynthesis for prevention from mucosal damage in food-sensitive enteropathy.