The following Food Allergies and Asthma Backgrounder will provide useful information on food allergies and asthma, including the definition of a food allergy and how it differs from a food intolerance, as well as food allergy symptoms, diagnosis, and management. Food additives, such as monosodium glutamate (MSG), are also covered. In addition, triggers of asthma, the role of food in asthma, and prevention of asthma are discussed.
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While allergy to pollen or other environmental sources typically causes a lot of discomfort during spring, summer, and fall, food allergy is one condition that knows no season. According to recent studies, approximately 12 million Americans—about four percent of adults and six to eight percent of children under the age of three—have a true food allergy.
People tend to diagnose themselves, believing they have allergic reactions to certain foods or food ingredients. Unfortunately, self-diagnosis of food allergy often leads to unnecessary food restrictions, nutrient deficiencies, and misdiagnosis of potential life-threatening medical conditions other than food allergy. Therefore, experts urge people to see a board-certified allergist for proper diagnosis.
What Is a Food Allergy?
A food allergy is an adverse reaction to a food or food component that involves the body’s immune system. A true allergic reaction to a food involves three primary components: 1) contact with a food allergen (reaction-provoking substance, virtually always a protein); 2) immunoglobulin E (IgE-an antibody in the immune system that reacts with allergens); and 3) mast cells (tissue cells) and basophils (blood cells), which when connected to IgE antibodies release histamine or other substances causing allergic symptoms.
The body’s immune system recognizes an allergen in a food as foreign and produces antibodies to halt the “invasion.” As the battle rages, symptoms appear throughout the body. The most common reaction sites are the mouth (swelling of the lips), digestive tract (stomach cramps, vomiting, diarrhea), skin (hives, rashes, or eczema), and the airways (wheezing or breathing problems).
Allergic reactions to food are rare and can be caused by any food. The most common food allergens, known as the “Big 8,” are fish, shellfish, milk, egg, soy, wheat, peanuts, and tree nuts such as walnuts, cashews, etc. Symptoms of a food allergy are highly individual and usually begin within minutes to a few hours after eating the offending food. People with true, confirmed food allergies must avoid the offending food altogether.
There are numerous misconceptions regarding allergy to food additives, preservatives, and ingredients. Although some additives and preservatives have been shown to trigger asthma or hives in certain people, these reactions are not the same as those reactions observed with food allergies. These reactions do not involve the immune system and therefore are examples of food intolerance or idiosyncrasy rather than food allergy. Most people consume a wide variety of food additives and ingredients daily, with only a very small number having been associated with adverse reactions.
There are also some adverse reactions to foods that involve the body’s metabolism but not the immune system. These reactions are known as food intolerance. Examples of food intolerance are food poisoning or the inability to properly digest certain food components, such as lactose or milk sugar. This latter condition is commonly known as lactose intolerance.
Life-threatening Reactions
Many allergic reactions to food are relatively mild. However, a small percentage of food-allergic individuals experience severe, life-threatening reactions, called anaphylaxis. Anaphylaxis is a rare but potentially fatal condition in which several different parts of the body experience foodallergic reactions simultaneously, causing hives, swelling of the throat, and difficulty breathing. It is the most severe allergic reaction.
Symptoms usually appear rapidly, sometimes within minutes of exposure to the allergen. Because they can be life-threatening, immediate medical attention is necessary when an anaphylactic reaction occurs. Standard emergency treatment often includes an injection of epinephrine (adrenaline) to open up the airways and blood vessels.
Diagnosing Food Allergy
Diagnosis usually begins with a thorough medical history, a complete physical examination, and selected tests to rule out underlying medical conditions not related to food allergy. Patients may also have to keep a food diary and record symptoms over a period of time.
Several tests are available to determine if a person is allergic to a certain food. In skin-prick testing, a diluted extract of the suspected food is placed on the skin, which is scratched or punctured. A blood test can provide information similar to skin testing. The gold standard for food allergy testing is the double-blind, placebo-controlled food challenge (DBPCFC). This test is performed by a board-certified allergist. The suspected allergen (e.g., milk, fish, soy) is placed in a capsule or hidden in food, and fed to the patient under strict supervision. Neither the allergist nor the patient is aware of which capsule, or food, contains the suspected allergen-hence the name “double-blind.” For the test to be effective, the patient must also be fed capsules or food that do not contain the allergen to make sure the observed reaction, if any, is to the allergen and not to some
other factor—hence the term “placebo-controlled.” These tests have enabled allergists to identify the most common allergens, and also to determine what foods and additives do not cause allergic reactions. These tests may also be used to determine if a child or individual has “outgrown” a certain allergy.
Managing Food Allergy
If a food allergy is diagnosed, the only proven therapy is avoidance of the offending food. Because there are no drugs or allergy shots on the market today to alter the long-term course of food allergy, elimination diets are prescribed. Each diet must consider the person’s individual nutritional needs—ability to tolerate the offending food, caloric needs, and other factors. Strict adherence to an elimination diet and careful avoidance of the food allergen may, in some cases, hasten the disappearance of the food allergy.
Most life-threatening allergic reactions to foods occur when eating away from the home. It is important to explain your situation and needs clearly to your host or food server. If necessary, ask to speak with the chef or manager.
Food Allergen Labeling
In January 2006, the U.S. Food and Drug Administration implemented the Food Allergen Labeling and Consumer Protection Act (FALCPA), requiring food labels to indicate if the product contains any of the “Big 8” allergens. Since food and beverage manufacturers are continually making improvements, food-allergic persons should read the food label for every product purchased, each time it is purchased.
Food Biotechnology and Food Allergies
Food biotechnology uses plant science and genetics to improve food and how it is produced. Today, biotechnology companies avoid using genetic material from plant foods commonly associated with allergies. Further, FDA regulations advise that companies that use genes from a known allergenic source should assume that they will produce an allergen, and test the food for allergenicity.
Biotechnology also is being used by researchers to remove allergens from foods. Experimental rice has already been modified to remove allergenic proteins, and work is underway to remove or neutralize allergenic proteins from other foods, such as peanuts or wheat. The future development of allergen-free foods may expand the choice of wholesome foods available to allergy sufferers.
Asthma and Food
What is Asthma?
Asthma, a chronic medical condition, affects more than 17 million Americans (three to four percent of the population). Asthma results when triggers (or irritants) cause swelling of the tissues to the air passages of the lungs, making it difficult to breathe. Typical symptoms of asthma include wheezing, coughing, and shortness of breath.
What are the Major Triggers of Asthma?
Asthma can be triggered by numerous factors, including allergens from dust, molds, pollen, animals, and, occasionally, food; air pollutants, such as cigarette smoke, auto exhaust, smog, or aerosol cleaners; colds and, particularly, respiratory infections; weather changes; exercise; or certain medications.
How Many Americans are Affected by Food-Triggered Asthma?
Food-triggered asthma is rare, occurring only among six to eight percent of children with asthma and less than two percent of adults with asthma.
Can Foods Trigger Asthma?
Only a few. For years it has been suspected that foods or food ingredients may cause or exacerbate symptoms in those with asthma. After many years of scientific and clinical investigation, there are very few confirmed food triggers of asthma. Sulfites and sulfiting agents in foods (found in dried fruits, prepared potatoes, wine, bottled lemon or lime juice, and shrimp), and diagnosed food allergens (such as milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish) have been found to trigger asthma. Many food ingredients such as food dyes and colors, food preservatives like BHA and BHT, monosodium glutamate, aspartame, and nitrite, have not been conclusively linked to asthma.
What Can Individuals with Asthma Do to Prevent a Food-Triggered Asthma Attack?
The best way to avoid food-induced asthma is to eliminate or avoid the offending food or food ingredient from the diet or from the environment. Reading ingredient information on food labels and knowing where food triggers of asthma are found are the best defenses against a food-induced asthma attack. The main objectives of an asthmatic’s care and treatment are to stay healthy, to remain symptom free, to enjoy food, to exercise, to use medications properly, and to follow the care plan developed between the physician and patient.
Originally printed in the 2007-2009 IFIC Foundation Media Guide on Food Safety and Nutrition
