This study investigated the utility of skin patch testing to identify delayed-type food hypersensitivities that trigger irritable bowel syndrome (IBS) symptoms. Using an extensive panel of type IV food allergens, patch testing was performed on individuals with IBS symptoms, after which patch test-directed avoidance diets were implemented in those patients with patch test reactions. All patients placed on avoidance diets were invited to participate in a questionnaire-based study assessing IBS symptom response to the diet. Primary end points included average abdominal pain during the more than 3-month food avoidance period and degree of improvement in overall IBS symptoms 3 or more months after initiation of the avoidance period. The results from this study add to the expanding body of evidence of a role for delayed-type food hypersensitivities in the pathogenesis of some cases of IBS. Skin patch testing to type IV food allergens offers a new approach to evaluating and managing these patients.