Adverse reactions to foods are either caused by immune-mediated or non-immune mediated response depending on whether the immune system is primarily involved in the cause of the reaction.  A common food allergy is immune-mediated reaction to egg, milk, soy, peanut, tree nut, shell fish and fish.  Reactions to foods that are not immune system responses are generally considered food intolerance.  Type of food intolerance includes toxins (poisons), metabolic, pharmacologic or other undefined reactions.  Almost all reactions to food additives are food intolerance and are chemical, not allergic reaction.

There are thousands of substances added to various foods for the purpose of coloring, flavoring, and preserving.   Of the thousands of additives used, only a handful has been identified as possible causes of adverse reactions.  It was estimated that the rate is probably less than 1% of adults, and up to 2% of children.  Food additive include the following group:  food dyes and coloring (such as tartrazine, annatto, saffron and carmine; emulsifiers and stabilizer (such as gums and lecithin); flavorings and taste enhancers (such as MSG, spices and sweeteners); preservatives (such as benzoates, nitrates and sulfites, sorbate); spices, sweetener (such as aspartame); and synthetic antioxidants (such as BHA).

Symptoms of food intolerance to additive vary in type and degree.  They depend on what kind of additive, the sensitivity of the patient, and the amount of additive.  People who react to one chemical are not likely reacting to others.   Many of the reactions to food additives are mild and resolve without treatment.  More severe reactions, including urticarial, angioedema, worsening asthma, and anaphylaxis may require immediate medical attention.

A reaction to food additives is suspected when a person experiences reactions to unrelated foods with common ingredients such as additives or when eating at restaurants, but not from foods prepared at home.   Most food additives cause a reaction that lasts less than one day.  If you suspect food additives are causing problems, remove the additive from your diet for a few days.  Your symptoms should promptly go away if the additive is the cause.  There are no specific allergy tests for food additive intolerance.  In many instances, the only way to truly diagnosis an adverse reaction to food additives is for a person to undergo an oral challenge with the suspected additive under close supervision of an allergist.

Most food additives are listed on the product label, along with other ingredients, in a descending order by weight (flavors are an exception and do not need to be identified).  Sometimes, the additive is spell out in full.  At other times, it is represented by a code number.  Read labels carefully and buy organic food products whenever you can.  Though more expensive than regular products, organically-produced food carries a much lower risk of containing food additive and dyes.