There are different mechanisms that play a role in the causation of adverse and undesirable effects triggered by the consumption of food. In the world of food allergies, It is important to distinguish between these mechanisms in order to arrive at an accurate diagnosis. Allergy, intolerance, and sensitivity to foods require different diagnostic approaches including a careful history and skin or blood testing in order to diagnose the condition. The management of these conditions also varies based on the underlying mechanisms.
An allergy to a food traditionally means that there is an immunologic reaction to proteins in that food. This reaction is usually mediated by specific antibodies (IgE antibodies or immunoglobulin E antibodies) to these proteins. These antibodies react with the protein antigens in the food. These reactions result in a release of chemical mediators such as histamine and tryptase from mast cells and basophils into the tissues and bloodstream.
These chemical mediators (e.g., histamine, tryptase) also have adverse effects on the blood vessels, heart, lungs, and other vital organs. The result of this release of chemical mediators could vary in severity from mild itching of the skin to a severe life threatening reaction such as anaphylaxis. Ingestion of even small amounts of food can trigger such reactions, which usually begin within minutes of exposure.
The most important element in diagnosing food allergies is taking a careful and comprehensive history from the patient. It is important for the board certified allergist to focus on the specific food ingested (including the list of ingredients in prepackaged foods) as well as the timeline of the onset and progression of the symptoms. The history is complemented by the detection of specific IgE antibodies to the food(s) in question by way of skin testing and/or blood testing. These specific IgE allergy tests should be limited to only the foods that could have triggered the reaction suggested by the history.
Treatment of food allergies traditionally has been focused on the identification and subsequent strict avoidance of the offending food(s). Patients are also prescribed an epinephrine auto-injector (e.g., EpiPen, Auvi-Q, Adrenaclick) to be used in case of a systemic reaction following an inadvertent exposure to the food. However, more recently, a desensitization procedure to foods such as peanuts by way of oral immunotherapy has become available.
As opposed to an allergy, an intolerance to a food is not mediated by an immunologic process. Instead, the process primarily involves the gastrointestinal system rather than the immune system. An insufficiency of certain enzymes usually found in the gastrointestinal system may hinder the proper digestive process and result primarily in gastrointestinal symptoms. A common example is lactose intolerance, where an enzyme called lactase is deficient. Lactose is a sugar found in dairy products. The enzyme lactase breaks down the lactose in normal individuals. In patients with lactose deficiency (i.e., lactose intolerance) the undigested lactose becomes fermented in the intestines which causes uncomfortable gastrointestinal symptoms such as nausea, abdominal discomfort, abdominal bloating, flatulence, and/or diarrhea after the consumption of dairy products. The symptoms are usually dose-dependent, meaning that the symptoms are usually worse the more you eat/drink.
Breath hydrogen tests are sometimes helpful in confirming the diagnosis of lactose intolerance. The treatment involves either avoidance of the foods one is intolerant to or supplementation with the oral enzymes (e.g., lactase enzyme) along with these foods in order to help in their digestion.
A sensitivity to a food is a poorly understood phenomenon and may involve non-specific inflammation of the gut. The symptoms are widely variable and may include abdominal pain, nausea, diarrhea, fatigue, joint pain, brain fog, and/or vague constitutional symptoms. The symptoms can begin hours or days after the food exposure and can be chronic in nature. The symptoms may be mediated by an immunologic processes but IgE antibodies are not usually involved. Some researchers speculate that IgG antibodies specific to foods may be involved, although it has not been scientifically proven. Interestingly, some IgG antibodies to certain foods can protect an individual from sensitivity and in fact, their levels are shown to rise after desensitization to those foods.
As the value of IgG antibodies in diagnosing food sensitivities has never been conclusively established, tests to measure IgG levels in blood against foods should not be ordered or obtained.
Of note, some physicians will lump food intolerance and food sensitivity into the same category.
Another caveat in the diagnosis of food allergies is that even elevated IgE antibody levels against specific foods do not always correlate with reactions after the consumption of these foods. False positives and false negatives can and do occur. Hence, the results should always be interpreted in the context of clinical reactions after exposure.
In view of the above mentioned nuances, ordering “broad panels” of specific IgE to various foods without correlating it to the patient’s history is not helpful in the diagnosis of food allergies. IgE levels should be obtained only to those specific foods that the patient could have reacted to, which should be based on the patient’s history. It is important to correlate the timeline of symptom onset as well as the progression of the symptoms after the exposure to the food.
The board certified allergists at Black & Kletz Allergy have 3 convenient office locations in the Washington, DC, Northern Virginia, and Maryland metropolitan area and are very experienced in the diagnosis and treatment of food allergy, food intolerance, and food sensitivity. Black & Kletz Allergy diagnose and treat both children and adults and have offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas, VA. We offer on-site parking at each location and the Washington, DC and McLean, VA offices are Metro accessible. There is a free shuttle that runs between the McLean, VA office and the Spring Hill metro station on the silver line. Please call our office to make an appointment or alternatively, you can click Request an Appointment and we will respond within 24 hours by the next business day. Black & Kletz Allergy has been serving the Washington, DC metropolitan area for more than 5 decades and we pride ourselves in providing exceptional allergy, asthma, and immunological care in a professional and pleasant environment.