Discrepancies between food content and label can lead to adverse reactions in people with hypersensitivity to particular food components. Over a 3‐year period, 20 occasions arose in Sweden where discrepancies between label and content were confirmed. In 14 cases the investigation was initiated because of adverse reactions observed by individuals with known disease. Analysis of the offending food included qualitative and quantitative antibody‐based techniques. The unexpected food ingredients were hazelnut, peanut, egg, milk, wheat, soy and chicken protein. The offending foods were chocolate, ice cream, meringue, lollypop, meatballs, sausage, hamburger, ham, kebabs, buns, pasta and buckwheat flour. Our study showed that simple immunological methods can be used for analysis of food protein for verification of contamination or mislabelling.