You can be intolerant to a food to which you are not "allergic". Food intolerance or sensitivity is much more common that food allergy. It estimated that somewhere between 6-10% of people are allergic to a food or foods but between 30-60% of people are intolerant to one or more foods or the additives or chemicals in food.
Food allergy testing will be negative if you are not allergic even though you are intolerant or sensitive to a food, additive or chemical. Food allergy is an abnormal immune response or reaction to a food protein. It is due to the same response to inhaled pollens or allergens. It results when the body makes a specific type antibody or immunoglobulin, known as IgE, to a food. When the food is eaten the IgE antibody recognizes the food protein as foreign and triggers the release of chemicals, especially histamine, from allergy cells in the body. This results in characteristic symptoms of swelling, itching, rash or hives, wheezing, shortness of breath, cough, low blood pressure and rarely death when the food is eaten.
Testing for food allergy consists of blood tests for the IgE antibodies (RAST) or the presence of a hive like reactions produced from histamine released at the site of skin prick, injection or patch contact with the food. The many food reactions that are not due to an allergic immune response involving IgE or histamine will have normal RAST IgE antibody levels and negative skin testing. Some of these food sensitivity or intolerance reactions are due to other antibodies such as IgA, IgM, or IgG. These antibodies may be detected in the blood, stool or saliva though such tests are not as well validated, accepted or available, especially in the U.S.
Diet treatments involving elimination of foods based on elevated IgG, IgM or IgA antibodies in the blood, evacuated stool samples, saliva or intestinal fluid retrieved from the body have shown mixed or to moderate success in people with rheumatoid arthritis and irritable bowel syndrome. The most well understood but still under recognized autoimmune food sensitivity with a genetic basis is gluten sensitivity, also known as Celiac disease. Non-celiac gluten sensitivity is much more common than Celiac disease but even less well recognized. Lactose intolerance is the most common food intolerance and often confused with the second most common food sensitivity, cow's milk protein or casein sensitivity. Gluten free casein free diet is now commonly employed as a treatment for autism. The medical community has generally been slow to accept gluten free casein free diet for autism, considering it unproven, though there is substantial scientific and experiential data to support this safe and often dramatically effective treatment.
Testing for IgG antibodies to foods in the blood is available from a few commercial laboratories. Saliva IgA antibody testing for foods is also available through several laboratories. These tests are generally not universally by health insurance and are often rejected as not valid or reliable by many doctors. Stool testing for IgA antibodies to gluten, tissue transglutaminase, dietary yeast, cow's milk protein (casein), soy, and chicken egg is available from Enterolab. This laboratory does not contract with any health insurance and most will not reimburse for the cost of testing. Most doctors either are unaware of this testing and either don't accept the tests as valid or don't know how to interpret the results.
Testing for mediator release (MRT) testing looks for an evidence of release of chemical mediators from immune blood cells triggered by foods, additives or chemicals. The presence of such a reaction is presumed to indicate sensitivity to such foods, additives or chemicals that can produce various symptoms and when substances producing such reactions are avoided or eliminated symptoms are suppose to improve significantly or resolve. MRT is available commercially through Signet Diagnostic Corporation (www.nowleap.com). Several insurance carriers pay for at least a portion of the cost of this testing however because it is considered "out of network" for most plans patients are usually responsible for payment of the service. Some carriers consider the testing "experimental" or not validated and therefore do not cover the testing.
The principle of MRT testing is that certain foods, additives and chemicals are capable of triggering non-allergy immune-based reactions. These reactions release various immune chemical mediators into the blood. If an immune reaction is triggered and these mediators are released, changes occur in the ratio of solids (cells) to liquid (blood serum) that can be measured. The white blood cells and platelets shrink and the volume of the liquid increases. The degree of change can be measured and reported as mild or moderate to severe corresponding with the degree of sensitivity to that particular food, additive or chemical.
Signet claims success with reducing or eliminating a myriad of symptoms or conditions including migraines, headaches, autistic behavior, anxiety, depression, ADD, sinus and ear, nose and throat problems, irritable bowel syndrome, vomiting syndromes, Celiac, chronic stomach aches, bladder problems, fibromyalgia, arthritis, eczema, hives, and chronic fatigue syndrome. The testing includes a comprehensive color report booklet containing a results specific diet plan with detailed information supplemented with several hours of personalized counseling from a dietician.
Of all the food intolerance or sensitivity testing MRT is the most broad and comprehensive. It looks for actual reaction produced by the body in response to foods or chemicals. Signet provides testing for 150 foods or chemicals (123 foods and 27 chemicals) including nitrates, nitrites, MSG and various food dyes. The limitation of all these tests is lack of universal acceptance by physicians and coverage by insurance. However, for those with suspected intolerance to foods or chemicals in whom available testing is negative or indeterminate, such testing can be quite helpful.