Recent research suggests that food allergies may not be as common as popularly thought. According to a May 2010 issue of the Journal of the American Medical Association, there have been few high quality studies conducted on food allergy prevalence in the U.S. and there is limited uniform criteria for properly diagnosis. [JAMA 2010;303[18]:1848-1856]. The JAMA study concluded that true food allergies probably affect more than 1% or 2% of the population, but less than 10%, below some popular claims.
Knowing the difference between a food allergy or a food intolerance can mean the difference between having to make extreme lifelong dietary changes, or simply watching one’s diet in the service of physical comfort and well-being.
Food Allergy or Food Intolerance?
The phrase “food intolerance” ["The Basics of Food Allergy and Intolerance," National Institute of Allergy and Infectious Diseases, 1999] refers to physiological reactions to food that do not involve the immune system. These responses can include:
- malabsorption problems due to enzyme deficiencies that produce things like lactose intolerance,
- reactions to naturally occurring chemicals in foods like salicylates in fruit,
- reactions to food contaminants like bacteria, and
- reactions to preservatives like sulfites, flavorings like monosodium glutamate, and colorants like tartrazine.
True "allergic" reactions to food involve the immune system, and can occur from very small amounts of the triggering food. Symptoms can include gastrointestinal distress, headaches, hives, and rashes or, in severe but rare cases, anaphylactic shock. Allergic reactions to food can occur immediately or up to many hours or days after ingesting the offending food or ingredient. The foods most likely to cause reactions in sensitive individuals are cow's milk, legumes (especially peanuts), some seafood, corn, eggs, wheat, and related grains like barley and rye, and finally tree nuts.
How Allergies Work
The immune system is, quite literally, a “body guard” comprised of specialized cells, proteins, tissues and organs whose sole job is to keep the body healthy and prevent infections caused by antigens, molecules the body identifies as dangerous. An allergic reaction is the series of events that occur within the immune system when an antigen is encountered.
Contact can include inhaling, eating or touching the antigen. When triggered, the immune system responds by attacking the antigen with antibodies, special proteins – in the case of allergies, Immunoglobulin (IgE) – to capture and consume the invaders, as well as by remembering what triggered the response in the first place, so that the immune system can protect against future encounters.
Different types of IgE antibodies can recognize and attack different types of allergy inducing invaders, ranging from cat dander to oak pollen and bee venom, in sensitive individuals. Why some people are allergic to things that bother no one else still isn’t completely understood, but reactions among allergic individuals are fairly predictable:
- “Mediators” like histamine and other chemicals from the mast cells common in the nose, eyes, lungs and intestines trigger tissue swelling, sneezing, wheezing, and coughing;
- Newly released mediators recruit other inflammatory cells, resulting in additional inflammation, causing excessive swelling and mucus production in those with chronic allergies.
The most severe, and potentially deadly, allergic reaction is anaphylaxis. Anaphylaxis is a rare, whole body allergic response in which a quick and voluminous release of mediators can cause a sudden and dramatic drop in blood pressure, constrict the airway and produce commensurate difficulty breathing, as well as nausea, vomiting and other symptoms. Estimates of those at risk for anaphylaxis have ranged widely from 1.21% to 15.04% of the population.
Identifying Food Allergies
The May 2010 JAMA report suggests that current methods for identifying food allergies create the potential for over-diagnosis. The principle methods for diagnosis are:
- a medically supervised food challenge, a process by which a doctor gives a patient samples of suspect foods and then observes any allergic reaction
- skin-prick test, where an extract of the potential allergen is place on the skin, and
- blood tests that look for food specific allergic antibodies (IgE).
However, the food challenge can be expensive, and the other two tests can produce false positives, with a less than 50% reliability rate in patients with non-specific symptoms like rash or gastrointestinal problems. JAMA researchers emphasized that patients suspecting food allergies should be seen by experienced clinicians who can distinguish between a food intolerance and a food allergy when evaluating diagnostic tests.
Doctors and patients will continue to mull over the ramifications of recent JAMA findings that food allergies may, in fact, be overly and improperly diagnosed. But being aware of the different categories of reactions – a non-immunological intolerance to a food, or an immunological food allergy – and the limitations of diagnostic methods can help patients make informed decisions about dietary changes, if needed.
In the end, the best advice is the most predictable: If a food allergy is suspected, visit an experienced clinician who knows the difference between food allergies and food intolerances.
Source:
American Academy of Allergy, Asthma and Immunology (AAAAI)
Theresa Willingham - My goal, as a writer and photographer, is to create thought provoking and informative content that inspires community engagement, and ...
