There is considerable confusion between allergy & intolerance.The term Allergy is used to describe those cases in which the adverse reaction to food occurs almost immediately, usually within 1 hour. The reaction is obvious & often quite violent, for eg. developing a swollen lip or tongue after eating peanuts, or becoming violently sick after eating shellfish. True food allergies are quite rare & affect only a small percentage of the population
The term Food Intolerance, on the other hand, affects a great number of people. The symptoms of food intolerance rarely occur immediately after the food is eaten. In fact, the reaction is usually delayed by many hours or even several days. For example, the cheese eaten on Monday could be the cause of Wednesday’s asthma attack or Sinusitis. It is these delayed reactions which make the detection of the culprit foods a very difficult task without the help of expert laboratory testing.