For more information refer to RPAH
Excerpt from Allergy Unit - RPAH:
The natural substances which can upset sensitive people are found in many different foods. The more of these consumed in the daily diet, the more likely it is that reactions will occur.
SALICYLATES are a family of plant chemicals found naturally in many fruits, vegetables, nuts, herbs and spices, jams, honey, yeast extracts, tea and coffee, juices, beer and wines. They are also present in flavourings (e.g. peppermint), perfumes, scented toiletries, eucalyptus oils, and some medications (ASPIRIN is a member of the salicylate family).
AMINES come from protein breakdown or fermentation. Large amounts are present in cheese, chocolate, wines, beer, yeast extracts and fish products. They are also found in certain fruits and vegetables, e.g. bananas, avocados, tomatoes and broadbeans.
GLUTAMATE is a building block of all proteins, and is found naturally in most foods. In its free form, not linked to protein, it enhances the flavour of food. This is why foods rich in natural glutamate are used in many meals, for example tomatoes, cheeses, mushrooms, stock cubes, sauces, meat extracts and yeast extracts. Pure monosodium glutamate (MSG) can also be used as an additive to increase the flavour of soups, sauces, Asian cooking and snack foods.
The foods most likely to cause problems are the tastiest ones, since they have the highest levels of natural chemicals.
People who are sensitive to natural food chemicals are usually also sensitive to one or more of the common FOOD ADDITIVES. The ones most likely to cause unpleasant reactions are listed (along with their code numbers) in the booklets mentioned above.