The aim of using oral and sublingual immunotherapy with food allergies is to enable the safe consumption of foods containing these allergens in patients with food allergies. In the present study, a systematic review of intervention studies was undertaken; this involved the searching of eleven international databases for controlled clinical trials. We identified 1152 potentially relevant papers, from which we selected twenty-two reports of twenty-one eligible trials (i.e. eighteen randomised controlled trials and three controlled clinical trials). The meta-analysis revealed a substantially lower risk of reactions to the relevant food allergen in those receiving orally administered immunotherapy (risk ratios (RR) 0·21, 95 % CI 0·12, 0·38). The meta-analysis of immunological data demonstrated that skin prick test responses to the relevant food allergen significantly decreased with immunotherapy (mean difference - 2·96 mm, 95 % CI - 4·48, - 1·45), while allergen-specific IgG4 levels increased by an average of 19·9 (95 % CI 17·1, 22·6) μg/ml. Sensitivity analyses excluding studies at the highest risk of bias and subgroup analyses in relation to specific food allergens and treatment approaches generated comparable summary estimates of effectiveness and immunological changes. Pooling of the safety data revealed an increased risk of local (i.e. minor oropharyngeal/gastrointestinal) adverse reactions with immunotherapy (RR 1·47, 95 % CI 1·11, 1·95); there was a non-significant increased average risk of systemic adverse reactions with immunotherapy (RR 1·08, 95 % CI 0·97, 1·19). There is strong evidence that orally administered immunotherapy can induce immunomodulatory changes and thereby promote desensitisation to a range of foods. However, given the paucity of evidence on longer-term safety, effectiveness and cost-effectiveness, orally administered immunotherapy should not be used outside experimental conditions presently.