For some highly reactive individuals, the underlying issue is their response to histamine. Histamine is an amine that is naturally occurring in certain foods and is also produced as a part of the fermenting process, therefore, making foods such as cheese and sauerkraut major sources. Only 1% of the population is affected by histamine, but if you are in that 1% your symptoms may be decreasing your quality of life considerably. Symptoms are wide ranged from hay fever, diarrhea, asthma, low blood pressure, hives, flushing to food sensitivities.
The primary cause of histamine intolerance is a defect in an enzyme called Diamine oxidase (DAO). Individuals with low DAO allow abnormal amounts of histamine to be absorbed, triggering their symptoms. The symptoms of histamine intolerance differ from those of food sensitivity in that they often occur immediately after eating these foods and the onset of this condition is often sudden and begins in middle age.
Testing may be done firstly through a trial of a low histamine diet. There is a blood test for DAO levels. A low DAO level indicates a likely histamine issue.