External exposed radiation may play an important role in pathogens of irritable bowel syndrome (IBS), although is thought to arise due to a combination of genetic and environmental factors. The result is dysregulated immune responses due to alteration in the gut microbiota population and the subsequent development of gut inflammation. It has recently been shown that the effect of ionizing radiation on T-cell lymphocytes might be a risk factor of IBS. This article tries to discuss the effects of low dose radiation on alternation in the population of beneficial members of the gastrointestinal tract flora. The result may be activated inflammatory response of mucosal immune status induced Toll like receptors. Lipopolysaccharides produced by most gram-negative bacteria of gastrointestinal tract play a role in the initiation and progress of the Toll like receptors in the intestines. Circulating cytokines and soluble receptors released by activated Th2 can regulate neuronal function via endocrine mechanisms. Disturbance of the cytokine-mediated interaction between cells may lead to neuronal dysfunction or sensory dysfunction, motor dysfunction, or both sensory and motor dysfunction in patient with IBS.