Pediatric & Adult Food Allergy
Over 50 million Americans have an allergy of some kind. Food allergies are estimated to affect eight percent of children and there to four percent of adults, according to the Centers for Disease Control and Prevention. Yet one in four (25%) people feel they have some type of food allergy. A potential explanation for this discrepancy is that a multitude of different types of adverse reactions to food can occur. Food allergy and food intolerance are two examples of the more common types of adverse reactions to food.
Food allergy symptoms are most common in babies and children, but they can appear at any age. You can even develop an allergy to foods you have eaten for years with no problems. Allergy testing can help distinguish between food intolerance and food allergy. Trust the Allergy & Asthma Center to help you determine if you are suffering from food allergy, food intolerance or some other type of adverse reaction to food.
What is a food allergy?
Like with all allergies, food allergy begins with the misidentification of a harmless protein by the immune system. The most common type of food allergy is caused by an overly sensitive immune system that creates IgE antibodies directed against an otherwise harmless protein in the food (allergens). Food allergy can be further divided into IgE-mediated (allergy antibody driven) reactions and non-IgE-mediated reactions.
Symptoms of an allergic reaction may involve the skin, the gastrointestinal tract, the cardiovascular system and the respiratory tract. They can can include one or more of the following:
- Vomiting and/or stomach cramps, or diarrhea
- Hives or swelling (angioedema)
- Shortness of breath
- Repetitive cough
- Shock or circulatory collapse
- Tight, hoarse throat; trouble swallowing
- Swelling of the tongue, affecting the ability to talk or breathe
- Weak pulse
- Pale or blue coloring of the skin
- Dizziness or feeling faint
- Anaphylaxis, a potentially life-threatening reaction that can impair breathing and send the body into shock; reactions may simultaneously affect different parts of the body (for example, a stomach ache accompanied by a rash) – anyone with allergy antibodies (IgE) to food is a risk for anaphylaxis
Most food-related symptoms start within two hours of ingestion; usually they start within minutes. In some very rare cases, the reaction may be delayed by four to six hours or even longer. Delayed reactions are most typically seen in individuals who develop gastrointestinal, non-IgE mediated food allergy (such as food protein-induced enterocolitis syndrome and eosinophilic gastrointestinal disorders) or children who develop eczema related to food and in people with a rare allergy to mammalian meat caused by the bite of a lone star tick.
While any food can cause an adverse reaction, eight types of food account for about 90% of all reactions:
- Tree nuts
Certain seeds, including sesame, sunflower and mustard seeds (the main ingredient in the condiment mustard), also are common food allergy triggers and considered a major allergen in some countries.
Tree nuts include: almond, Brazil nut, cashew, hazelnut, macadamia nut, pecan, pine nut, pistachio and walnut
Shellfish can include: crustaceans (e.g. shrimp, lobster, crab) and mollusks (e.g. scallops, clams).
What is cross-reactivity?
People allergic to a specific food may also have a reaction to related foods. A person allergic to one tree nut may be cross-reactive to others. Those allergic to shrimp may react to crab and lobster. Someone allergic to peanuts - which actually are legumes (beans), not nuts – may have problems with tree nuts, such as pistachios and cashews, pecans or almonds; in very rare circumstances they may have problems with other legumes (excluding soy). In addition, the proteins in cow’s milk are very similar to the protein in other mammal’s milk. So, there is about a 90% chance that if you are allergic to cow’s milk, the milk of sheep or goats may also cause an allergic reaction due to cross-reactivity.
Learning about patterns of cross-reactivity and what must be avoided is one of the reasons why people with food allergies should receive care from a board-certified allergist. Determining if you are cross-reactive is not straightforward. Allergy testing to many items in the same “family” may not be specific enough – many times, these tests are positive, given how similar two food items in a “family” may look to the test even if you are not truly allergic. If you have tolerated it well in the past, a food that is theoretically cross-reactive may not have to be avoided at all.
Another type of food allergy caused by cross-reacting IgE antibodies is the Oral Allergy Syndrome (also called the Pollen-Fruit Syndrome and Pollen-Food Allergy Syndrome). With this condition, symptoms are triggered due to cross-reactivity between plant proteins from pollen and fruits or vegetables.
Because cross-reactivity makes identifying triggers difficult, you need the expertise of medical professionals like those at the Allergy & Asthma Center to perform complete testing.
How are food allergies diagnosed?
Once you are allergic to a food, you will usually experience some sort of reaction every time the trigger food is eaten. Symptoms can vary from person to person, and you may not always experience the same symptoms during every reaction. It is impossible to predict how severe the next reaction might be, and all patients with IgE type food allergy are at risk of anaphylaxis.
To make a diagnosis, you will be asked detailed questions about your medical history and your symptoms. These questions will likely include:
- What and how much you ate
- How long it took for symptoms to develop
- What symptoms you experienced and how long they lasted.
- After taking your history, we may order skin tests and/or blood tests, which indicate whether food-specific immunoglobulin E (IgE) antibodies are present in your body:
- Skin-prick tests provide results in about 20 minutes.
Blood tests, which are a bit less exact than skin tests, measure the amount of IgE antibody to the specific food(s) being tested. Results are typically available in about a week and are reported as a numerical value.
Your allergist at the Allergy & Asthma Center will use the results of these tests in making a diagnosis. A positive result does not necessarily indicate that there is an allergy, though a negative result is useful in ruling one out.
In some cases, we may recommend an oral food challenge, which is considered the most accurate way to make a food allergy diagnosis. This test is helpful when the reaction history is unclear or if the skin or blood tests are inconclusive. It also can be used to determine if an allergy has been outgrown.
Because of the possibility of a severe reaction, an oral food challenge should be conducted only by experienced allergists in our office, with emergency medication and equipment on hand.
How is food allergy different from food intolerance?
The immune system is not directly involved in food intolerance. Food intolerances have various causes. For example, a person may lack an enzyme needed to digest a portion of a certain food (e.g. lactose intolerance) or the food may be contaminated by bacterial or other toxins that cause symptoms resembling those of food allergy (e.g. food poisoning).
Symptoms of food intolerance often mimic food allergy, so testing is important to distinguish the two. Symptoms of food intolerance can include:
How is food allergy treated?
The primary way to manage a food allergy is to avoid consuming the food that causes you problems. We strongly recommend that you carefully read ingredient labels of all food products to verify that your food allergen(s) are not listed. We also recommend that you learn whether what you need to avoid is known by other names.
The Food Allergy Labeling and Consumer Protection Act of 2004 (FALCPA) mandates that manufacturers of packaged foods produced in the United States identify, in simple, clear language, the presence of any of the eight most common food allergens - milk, egg, wheat, soy, peanut, tree nut, fish and crustacean shellfish - in their products. The presence of the allergen must be stated even if it is only an incidental ingredient, such as an additive or flavoring.
Some foods are labeled with precautionary statements, such as “may contain,” “might contain,” “made on shared equipment,” “made in a shared facility” or some other indication of potential allergen contamination. There are no laws or regulations requiring those advisory warnings and no standards that define what they mean. If you have questions about what foods are safe for you to eat, talk with your allergist.
You should know that the FALCPA labeling requirements do not apply to items regulated by the U.S. Department of Agriculture (meat, poultry and certain egg products) and those regulated by the Alcohol and Tobacco Tax and Trade Bureau (distilled spirits, wine and beer). The law also does not apply to cosmetics, shampoos and other health and beauty aids, some of which may contain tree nuts and/or seed extracts or wheat proteins.
Avoiding an allergen can be very challenging. While labeling has helped make this process easier, some foods are so common that avoiding them is daunting. A dietitian or a nutritionist may be able to help. These food experts will offer tips for avoiding the foods that trigger your allergies and will ensure that you still will be getting all the nutrients you need in your diet. Special cookbooks and support groups, either in person or online, for patients with specific allergies can also provide useful information.
At the Allergy and Asthma Center, we recognize that all patients with IgE-mediated food allergy have the potential with exposure to develop a life-threatening anaphylactic reaction. Therefore, we strongly recommend that all patients with this type of food allergy have an epinephrine auto-injector available at all times. We provide all patients who have IgE-mediated food allergy with a Food Allergy and Anaphylaxis Emergency Care (FARE) Plan, to help guide treatment if/when these reactions develop.
Many people with food allergies wonder whether their condition is permanent. There is no definitive answer. Allergies to milk, eggs, wheat and soy often disappear over time, while allergies to peanuts, tree nuts, fish and shellfish tend to be lifelong.
More recently, research has shown that with certain food allergies (cow’s milk and egg), baked forms of these food proteins are often tolerated by the immune system. Furthermore, once it is established that people tolerate these extensively heated proteins (after an office-based oral food challenge), the introduction of these “baked” forms of cow’s milk or egg protein into the diet on a regular basis may help with the development of long-term tolerance.
Lastly, a growing area of intense research with regards to food allergy is currently underway. Symptoms associated with the Oral Allergy Syndrome often improve with immunotherapy for the appropriate pollen. Immunotherapy for all other forms of food allergy is not yet approved by the Food and Drug Administration (FDA). However several promising clinical trials looking at food allergen patches and oral immunotherapy for certain foods have been conducted and are still underway. Look to your specialist at the Allergy and Asthma Center for the most current, cutting-edge medical care.