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 Food allergy is the most common cause of anaphylaxis outside of the hospital.1,2 Experts estimate that from 2% to 2.5% of the general population, or 5.4 to 7 million Americans have food allergies.3 About 3 million of these are believed to be allergic to peanuts or tree nuts alone.3 Food allergy is an increasingly common cause of anaphylaxis that results in about 125 deaths each year in the United States.4 Some allergists believe that this perceived rise in incidence may be attributed to children's increased exposure to certain foods, such as peanuts, before their immune systems are mature enough to handle them.5,6 Most food allergies are caused by eight common foods. Some of the symptoms of an allergic reaction to foods may resemble a food intolerance, and it often takes a skilled physician to diagnose a food allergy. Once diagnosed, a physician should guide the patient to the best treatment and prevention practices. Having a food allergy, as with any other severe allergy, means that a person's immune system reacts to a protein, in this case in food, as a threatening foreign substance and primes the body's defenses against it by producing IgE antibodies. IgE antibodies, once formed, attach to tissue mast cells on body surfaces so that they stand ready to react when the allergen is reintroduced. On re-exposure to the allergen, mast cells release mediators (histamine, chemotactic factors) or cause the formation of other mediators (prostaglandins, leukotrienes) in the surrounding tissue. The mediators are responsible for producing the immediate symptoms of an allergic reaction.9 Late-phase allergic reactions occur when eosinophils and other cells are attracted to the affected region.9 Eosinophils are leukocytes that can drive IgE production in allergic responses and also can release cytokines. There are eight types of foods that are accountable for 90% of all food-allergic reactions.7,9 The foods that most commonly cause anaphylaxis (called allergenic foods) are:
Sulfites added to foods can also set off anaphylactic reactions, as well as exercising, within a few hours after eating for a small number of people who do not otherwise experience food-related anaphylaxis. Children, who have immature immune systems, are most susceptible to a broad array of food allergies. People have been known to outgrow allergies to milk, soy, and eggs after childhood. However, peanuts, tree nuts, and shellfish allergies tend to be lifelong.5,8,9 In fact, the reactions to these foods may become more serious over time. In any case, when sensitivity exists, the intensity of a given anaphylactic attack is unpredictable because it depends on:
Also, if someone already has another immune problem, he or she may be at increased risk for a strong reaction to the food to which he or she is allergic. For example, patients who have asthma or atopic dermatitis, as well as food allergies, are at increased risk for severe anaphylaxis.1,2,10,11 The symptoms of food allergies can range from mildly irritating to life threatening. The most common are:
Other symptoms typical of anaphylaxis generally include:
For some people with food allergies, just a taste or even a touch of the foods to which they are allergic can result in any of these symptoms and can set off a chain reaction that takes only minutes to culminate in full-blown anaphylaxis: swelling of the airways, loss of blood pressure, loss of consciousness, shock, and even death.12 This can happen with their first exposure to a food. There have even been cases in which inhalation exposure to a food has triggered an anaphylactic reaction.13 The more rapidly symptoms present themselves; the more likely the reaction is to be severe.13 Food allergy and intolerance are often mistaken for each other. While they may share similar symptoms, including diarrhea and vomiting, food allergy is an immune system response and food intolerance occurs when the digestive tract reacts adversely to a food. For example, one of the most common food intolerances arises in response to lactose, the sugar in milk. Lactose intolerance occurs when a person lacks an enzyme, lactase, that is needed to digest this sugar, and the body reacts with gas, bloating, diarrhea, and abdominal pain when milk products that contain lactose are consumed. When these symptoms occur as a result of intolerance rather than allergy, they do not indicate an anaphylactic reaction. However, anyone who has such symptoms should seek medical care to get a diagnosis and counseling in order to determine what dietary and medical measures are needed. A person who has experienced even mild allergic reactions to food should seek a diagnosis by a board-certified allergist (direct your patients to Find an Allergist to locate an allergist near you). To make a proper diagnosis, the allergist will record a complete history of the symptoms, which foods were eaten, how much of the food was eaten, and how soon afterward the symptoms began. The doctor may also perform a skin prick test, RAST (radioallergosorbent test), or oral food challenge to confirm the diagnosis. In vitro testing with RAST or ELISA for IgE to food proteins is the safest diagnostic procedure. Food challenges are generally reserved for patients with unclear in vitro diagnostic results or when identification of the food allergen is deemed to be life saving.13 In most cases, there is no cure for food allergies. Therefore, it is essential that people with food allergies protect themselves by carefully avoiding the foods that trigger their reactions, and by being prepared to immediately treat anaphylactic reactions that do occur with epinephrine, followed by emergency medical care.
Avoidance Since it is often difficult to avoid hidden foods—and because it is often difficult for children to resist sharing foods—it is important that an allergic person's family, friends, and teachers know about and understand the ramifications of food allergy so that they can aid in preventing anaphylaxis and be ready to assist should an emergency arise.
Epinephrine A 1992 study in children and adolescents with food allergy, which was published in the New England Journal of Medicine, shows how important it is for people with food allergies to carry epinephrine at all times.10 According to the study, 10 of 13 fatal and near-fatal anaphylactic reactions to food occurred in public places, and none of the adolescents and children who died had epinephrine with them. All of the adolescents and children who survived received epinephrine before or within 5 minutes after the development of severe symptoms.10 Other studies corroborate these findings.11 Thus, all food-allergic individuals should carry self-injectable epinephrine, such as EpiPen® or EpiPen® Jr epinephrine auto-injectors, with them at all times. Since immediate administration of epinephrine can mean the difference between life and death, the parents of children with life-threatening food allergies should alert their child's school of the particular allergen, and make sure that their child's teachers and caregivers have an epinephrine auto-injector on hand and know how to use it. The side effects of epinephrine may include palpitations, tachycardia, sweating, nausea and vomiting, and respiratory difficulty. Cardiac arrhythmias may follow the administration of epinephrine. Therefore, the physician should instruct the patient about the circumstances of which this life-saving medication should be used. Physicians should also instruct their patients about whether antihistamines should be carried in addition to epinephrine. Wearing a medical identification bracelet describing the patient's allergies and susceptibility to anaphylaxis can help ensure prompt, proper treatment during an emergency.
Emergency medical care
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