A new study published in Immunity, Inflammation and Disease elucidated the immune mechanism underlying the mucosal inflammation in irritable bowel syndrome (IBS)—focusing on dental metal hypersensitivity—a T cell-mediated, delayed-type allergic reaction that causes oral contact mucositis and systemic cutaneous inflammation.This pilot study included 147 Japanese IBS patients and 22 healthy controls (HCs) who underwent the in vitro lymphocyte stimulation test to quantify their sensitivity to zinc, gold, nickel and palladium – metals commonly used in dentistry.The results revealed that 56.5% of the IBS patients were hypersensitive to at least one metal species, whereas 31.8% of HCs were hypersensitive to only a single metal species. The overall incidence of metal hypersensitivity was significantly higher for IBS patients than for HC. Moreover, a significantly higher proportion of IBS patients were hypersensitive to zinc and/or nickel. Additionally, the severity of the sensitivity to zinc and nickel was significantly greater for IBS patients than for HC. On the other hand, there was no significant difference in the sensitization rates and the sensitivity among the IBS subtypes.Hence, the findings indicated that IBS patients have a markedly higher prevalence of hypersensitivity to zinc and nickel, suggesting the possible involvement of dental metal hypersensitivity in the IBS pathogenesis in this population.