Intolerances to foods can cause problems such as bloating, stomach cramps, vomiting, diarrhoea and fatigue. Symptoms usually occur several hours after eating. Food intolerances are not allergies because they do not involve the immune system, but can be mistaken or self-diagnosed as allergies.

People with intolerances can usually eat small amounts of the foods to which they are intolerant. In contrast, allergic reactions to foods usually occur quickly and can be life-threatening. People with allergies to foods usually react to small amounts of the food.