The recently discovered Th9 subset and associated IL‐9 secretion were found to be involved in food allergy and especially in peanut allergies.63 IL‐9 is mainly responsible for the production of IL‐4 by Th2 cells to promote mucosal mast cell accumulation and secretion of mucus and chemokines by epithelial cells to sustain allergic inflammation.64 To a lesser extent, γδT cells found in the intestinal epithelium and in the lamina propria were also shown to be involved in food allergy. This evidence concerns the gene IL9 and peanut allergic reaction.