Food intolerance can generally be understood as an abnormal reaction of the organism to certain food components. There are food intolerances and intolerances to various components of food - to sugars such as lactose or fructose, but also to histamine or certain protein components of food. However, a conceptual distinction must be made here: Intolerances are due to an insufficient enzymatic digestive process. Intolerances to protein components are an above-average reaction of the immune system (usually due to a permeable intestinal mucosa).