The pathogenesis of ulcerative colitis (UC) is unclear. House dust mite (HDM) is associated with immune inflammation in the body. This study is designed to identify the association between HDM and UC clinical symptoms. UC patients (n = 86) and non-UC control (NC) subjects (n = 64) were recruited. Colon lavage fluids (CLF) were collected from HDM skin prick test positive patients during colonoscopy, and analyzed by immunological approaches. HDM was detected in fecal samples, which was positively correlated with UC clinical symptoms. HDM-specific eosinophils and Th2 cells were detected in CLF, which could be specifically activated by exposing to HDM in the culture. Direct exposure to HDM induced eosinophil activation in the colon of UC patients. UC patients displayed elevated levels of Th2 cytokines in the serum. UC clinical symptom scores were positively correlated with serum levels of Th2 cytokines. HDM was detected in UC patients’ stools, which was positively correlated with UC clinical symptoms. Direct exposure to HDM could trigger eosinophilic activation of the colon.
