A number of studies reported low-grade inflammation as another mechanism implicated in IBS, in which higher infiltration of cytokines e.g., IL-4, IL-6, or TNF-α, pro-inflammatory mediators and mast cells in the colonic mucosa impairs the tight junctions complexity and thus exacerbates IBS symptoms (Camilleri et al., 2012). Here, IL4 is linked to irritable bowel syndrome.