Peanut allergy is a severe and life-threatening form of food allergy. Treatments are being developed but the mainstays of current management remain avoidance of peanut and appropriate use of rescue medication. We report the case of a boy with peanut allergy who required a bone marrow transplant (BMT) for combined immunodeficiency. A food challenge, 2 years after transplant, showed that his peanut allergy had resolved. Allergic disorders constitute a form of immune deviation and while we do not advocate BMT as a treatment for peanut allergy, we believe this case provides an insight into the basic mechanisms involved in food allergy.