IgG-dependent allergy may be one of the causative or perpetuating factors for gastrointestinal diseases, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). Reactions in which IgG antibodies are involved result in more delayed responses compared to IgE-dependent allergy. Abnormal IgG-dependent reactions to food lead to the formation of immune complexes and, as a result, to the development of chronic inflammation. In spite of that, IgG-dependent allergy is considered controversial, as some scientists consider these reactions physiological. An elimination diet based on the results of IgG testing against specific food antigens is be­neficial in the treatment of IBS and IBD.