If the history and tests are inconclusive, then an exclusion of suspected foods, or of common allergenic foods may be useful, especially if non-IgE-mediated or non-immune-mediated reactions are suspected. This should be undertaken under the guidance of a dietitian and only for a set period of time, not exceeding 6-8 weeks. Re-introduction of these foods can often be done at home, but where IgE-mediated food allergy is suspected, or severe reactions have been experienced, then this should be undertaken in hospital as a re-introduction or oral food challenge.