Food allergies and intolerances (1/5): allergy or intolerance?

To food allergies and intolerances, many of us are concerned, even if sʹit is difficult to put an exact figure on the number of people who suffer from them. What are the causes of this phenomenon? Which foods pose a problem? What solutions are emerging? allergy' and 'intolerance'. How can we tell them apart and, above all, how can we identify them?