Food intolerances are part of a broader group of disorders known as adverse food reactions. Food intolerances are more common than food allergies and, unlike allergies, are not caused by an immune system reaction.
The first observations of abnormal responses to an ingested food were made in ancient times. Hippocrates, for example, described adverse reactions to the ingestion of cow’s milk. However, adverse food reactions continue to be one of the most controversial areas of medicine: the underlying mechanisms are not fully understood, and there is still a great deal of uncertainty over clinical symptoms, diagnosis and diagnostic tests. As a result, opinions differ as to how common these disorders are and on their social impact.