Summary Background Adverse reactions to food include immune mediated food allergies and non‐immune mediated food intolerances. Food allergies and intolerances are often confused by health professionals, patients and the public. Aim To critically review the data relating to diagnosis and management of food allergy and food intolerance in adults and children. Methods MEDLINE, EMBASE and the Cochrane Database were searched up until May 2014, using search terms related to food allergy and intolerance. Results An estimated one‐fifth of the population believe that they have adverse reactions to food. Estimates of true IgE‐mediated food allergy vary, but in some countries it may be as prevalent as 4–7% of preschool children. The most common food allergens are cow's milk, egg, peanut, tree nuts, soy, shellfish and finned fish. Reactions vary from urticaria to anaphylaxis and death. Tolerance for many foods including milk and egg develops with age, but is far less likely with peanut allergy. Estimates of IgE‐mediated food allergy in adults are closer to 1–2%. Non‐IgE‐mediated food allergies such as Food Protein‐Induced Enterocolitis Syndrome are rarer and predominantly recognised in childhood. Eosinophilic gastrointestinal disorders including eosinophilic oesophagitis are mixed IgE‐ and non‐IgE‐mediated food allergic conditions, and are improved by dietary exclusions. By contrast food intolerances are nonspecific, and the resultant symptoms resemble other common medically unexplained complaints, often overlapping with symptoms found in functional disorders such as irritable bowel syndrome. Improved dietary treatments for the irritable bowel syndrome have recently been described. Conclusions Food allergies are more common in children, can be life‐threatening and are distinct from food intolerances. Food intolerances may pose little risk but since functional disorders are so prevalent, greater efforts to understand adverse effects of foods in functional disorders are warranted.

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