What is a food intolerance?
Food allergies are relatively uncommon compared to what are regarded as food intolerances, with one in five adults self-reporting that they have a food intolerance.1,5
Rather than being an IgE response with an immediate reaction, food intolerances have been described as a non-allergenic hypersensitivity.8 Symptoms have a slower onset (4-24 hours) than IgE- moderated responses, which may mean it is initially harder to identify which food is involved, if any.1,3
Reactions may be T-cell mediated.3 Rashes may occur, and other common symptoms include fatigue, bloating, stomach cramps, an "irritable bowel", eczema, joint pain, or migraine.
However, these symptoms are also present in long-term conditions such as arthritis, eczema, irritable bowel syndrome, ME/chronic fatigue syndrome, and ulcerative colitis. These are not necessarily linked to food intolerance, but food may exacerbate an underlying condition.1,5
Cow's milk is the most commonly self-reported food allergy,9 but lactose intolerance is caused by the inability to digest lactose due to an insufficiency or absence of the enzyme lactase in the gastric tract. Rather than an allergic response, bacterial fermentation of milk in the colon leads to gastric symptoms such as flatulence, bloating or diarrhoea.10
Coeliac disease affects about 1 per cent of the population. It is not regarded as an allergy or a gluten intolerance, but an auto- immune disease triggered by gluten proteins found in wheat, barley and rye.11