Food Allergy, Sensitivity, and Intolerance

Note: This article is not meant as a substitute for proper medical advice. Please consult with your medical practitioner before using any type of remedy, herbal or otherwise.

To learn more:

 

By Robert Luby, MD

It’s easy to get confused when it comes to adverse reactions to foods as the medical community itself is laden with controversy in this area. The terms “allergy”, “sensitivity”, and “intolerance” are too often used interchangeably or without precision. This article will attempt to clarify what has become a very perplexing situation.

Allergies, by definition, must be caused by a reaction of the immune system. Food allergies must, therefore, involve an immune response to a food. Too often in the public realm any adverse reaction to a food is labeled an “allergy” when in fact there is no immune system involvement. In the medical world the situation is different.  Research indicates that there may be at least four types of immune responses to food. Three of these involve different types of antibody response (IgE, IgG, and IgA antibodies), while the fourth appears to be a white blood cell response which does not rely on antibodies. Most conventional medical practitioners regard only IgE antibody responses as true allergies and either do not believe in the existence of the other three, or imprecisely classify them as “intolerances” or “sensitivities”.

IgE allergies are the most dangerous, and can involve local swelling due to the action of histamine. This can result in swelling of the throat, difficulty breathing, anaphylaxis, and death.  Allergy specialists can readily test for this type of allergy. The most common food inducers of IgE-mediated allergic responses are peanuts, dairy, cereal grains (especially wheat/gluten), tree nuts, eggs, soy, shellfish, seeds, citrus fruit, food preservatives and coloring.

The IgG, IgA, and white blood cell-mediated reactions to food are less well-studied and much more controversial.  Unlike adverse IgE responses, which usually occur rapidly after ingestion of the offending food, these reactions are more subtle and may take several days to manifest. They appear to most commonly involve adverse intestinal and abdominal symptoms, skin findings (especially rashes), or mucus membrane effects (canker sores in the mouth, for example).  But they may also involve fatigue, irritability, or other vague responses.  The testing for these types of reactions is in its infancy and the reliability is such that the “gold standard” for determining this type of response is the “elimination diet with reintroduction”. This involves eliminating the suspected offending food (usually for at least one month), and then reintroducing the food and monitoring for symptoms.

The most oft-quoted definition of “food intolerance” is the lack of enzymes needed to digest the food.  Lactose intolerance is associated with insufficient lactase, which is the enzyme necessary to digest the primary sugar found in dairy products (lactose). This is different from casein intolerance, which is the adverse response to the main dairy protein.  Exemplary of the lack of clear cut definitions in this field is celiac disease.  This condition involves a lack of enzymes to fully digest gluten (a major protein in wheat, rye, barley, kamut, spelt, and possibly oats). But it also involves an immune response, not against the food itself, but against the lining of the intestine. There is clearly more involved here, as many celiac patients have neurological and other manifestations beyond the intestines.

“Food sensitivity” is the least well-defined term and the least understood. By the process of elimination, it is generally considered to be an adverse reaction to food which does not involve an immune response or a lack of digestive enzymes.  The manifestations of the reaction may present in innumerable symptoms, and the severity and reproducibility of the symptoms with ingestion of the food are highly variable.  Apart from foods themselves, other common offenders include sulfites, phenols, salicylates, MSG (monosodium glutamate), preservatives, colorings, texturizers, stabilizers, and other additives.

The potential for adverse reactions to genetically modified foods is a very controversial topic beyond the scope of this article. The most common claims made against genetically modified foods involve allergies, infections, cancers, antibiotic resistance, and a variety of chemically toxic effects. It is an area of intensive research, and future findings may conclude that allergy, intolerance, and sensitivity are all involved.