<p>Leukotriene B4 receptor type 1 (BLT1), a high-affinity receptor for leukotriene B4 (LTB4), plays an important role in inflammatory responses, including allergic airway inflammation. In this study, we examined the effect of genetic BLT1 deletion (KO) on ovalbumin (OVA)-induced allergic enteritis, a gastrointestinal form of food allergy in mice. Repeated oral OVA challenges after sensitization with OVA/alum induced allergic enteritis, characterized by systemic allergic symptoms (scratching, immobility, and swelling), diarrhoea, colonic oedema, and colonic goblet cell hyperplasia, accompanied by increased colonic peroxidase activity, colonic inflammatory cytokine expression, and serum OVA-specific IgE levels. The severity of enteritis was significantly attenuated in KO mice compared with wild-type (WT) mice, without an increase in serum OVA-specific IgE levels. The accumulation of neutrophils, eosinophils, M2-macrophages, dendritic cells, CD4+ T cells, and mast cells was observed in the colonic mucosa of allergic enteritis, and such accumulations were significantly lower in KO mice than in WT mice. BLT1 expression was upregulated and colocalized mostly in neutrophils and partly in eosinophils and dendritic cells in the colonic mucosa of allergic enteritis. These findings indicate that BLT1 deficiency ameliorates OVA-induced allergic enteritis in mice, and that LTB4/BLT1 contributes to neutrophil and eosinophil accumulations in the allergic colonic mucosa. BLT1 is therefore a promising drug target for the treatment of food allergies.</p>