Reactions to lactose are in general related to intolerance and not to an allergy. However, lactose is seldom a pure sugar. Contamination of lactose with milk proteins could trigger allergic reactions in children that are highly allergic to cow’s milk proteins (the allergenic threshold to cow’s milk proteins could be in the order of micrograms). Mandatory labelling of lactose, milk and milk products, allows people to identify those components in their diet.