Amines are naturally occurring chemicals found in many foods. They result from the breakdown of proteins or through the fermentation process, and are responsible for giving the food its flavor. The more intense the flavor, the higher the amine content, so the longer, say, a fruit ripens or a meat cures the more amines it will contain.
A complete list of high amine foods is available on the website, but the highest amounts can be found in aged cheeses, chocolate, wine, many alcoholic beverages, aged meats such as sausage or salami, canned or smoked fish, banana, avocado, and tomato. Amine content increases as certain fruits ripen and as meats and fish age, so those sensitive should only consume the freshest produce, meats and fish.
When you eat a food high in amines, the histidine it contains is metabolized by enzymes and bacteria to amines which are quickly absorbed in the gut and, in people who are sensitive, an allergy-type of response occurs. The end result is widening of blood vessels, tissue inflammation and swelling just as our own natural histamine creates.