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What is a Food Allergy?

Like so many other daily concerns involving scientific research, experts have yet to come to an agreement on the exact definition for food allergy.  They generally recognize a food allergy as the immune system responding to an otherwise harmless food as if it were a threat. But not all immune responses are created equally.

In order to be recognized as a true food allergy, a protein within a particular food item prompts the body to create a specific kind of antibody known as immunoglobulin E (IgE). Upon first exposure to the allergen, the body reacts by creating IgE antibodies which are specifically sensitized to that particular food protein, or allergen. These IgE antibodies then attach themselves to mast cells. Mast cells are responsible for healing wounds and defending the body against invaders such as allergens and pathogens.

Once IgE antibodies are sensitized or familiar with the allergen and attached to mast cells, any subsequent ingestion of the offending allergen will cause the IgE antibodies to stimulate mast cells into releasing chemicals such as histamine. This results in the classic, observable symptoms of allergic reaction. The area of the body where the stimulated mast cells reside, and where they release histamine during this process determines the type and severity of allergic symptoms.


The symptoms of a food allergy can range from mild to severe. An affected person could experience itching or tingling in the mouth, swelling in their lips, face, tongue and throat, hives, difficulty breathing, or gastrointestinal complications, including vomiting, diarrhea or abdominal pain.

In some cases, food allergies can result in anaphylaxis, a very severe allergic reaction which often occurs within minutes of a person consuming the offending food. Anaphylaxis can cause difficulty breathing, swelling of the lips, tongue and face, a sudden drop in blood pressure and possibly a loss of consciousness.

A mild reaction to an offending food on previous occasions does not exclude anaphylaxis as a possible response if a person is exposed to that food again. Similarly, if a person experiences anaphylaxis following exposure to an offending food, they are not necessarily more likely to experience anaphylaxis if they encounter the food a second time. If left untreated, anaphylaxis can result in death.

The Worst Offenders

Peanuts, tree nuts, milk, eggs, wheat, soy, fish and shellfish account for about 90 percent of all allergic reactions, though numerous other foods have been documented as causing IgE-mediated allergic reaction. In the last year alone, undeclared allergens in food accounted for 196 food recalls in the United States and Canada, or about 23 percent of all recalls according to our data at Food Sentry.

The allergens in foods are usually major naturally occurring proteins and are resistant to various forms of processing including, heat processing, such as in cooking.

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Any food containing protein has the potential to elicit an allergic reaction. It is possible that the availability of foods within a certain geographical area plays a role in what foods commonly cause allergic reaction. For instance, buckwheat allergies are common in Southeast Asian countries, celery allergy is common in European countries, and sesame seed allergy is common in Middle Eastern countries and in areas with large Middle Eastern populations.

Who is at Risk?

Various types of allergies and allergic diseases, such as asthma and eczema, have a genetic component; food allergies are no different. According to Dr. Scott Sicherer of the Mount Sinai Medical Center and Chief of the Division of Pediatric Allergy and Immunology, children who have parents who suffer from allergies, either food, pharmaceutical, or environmental allergies, are at an increased risk of developing allergies. That risk is even greater if both parents suffer from allergies. The type of allergy that manifests is not genetically controlled, however, so children of parents with pet dander allergies can develop a food allergy just as easily as a child with parents who suffer from food allergies.

According to a study published in the journal Pediatrics in July 2011, food allergy prevalence among children in the United States was 8 percent, and 39 percent of children with food allergies have had a severe allergic reaction. Another study published in the journal Clinical Pediatrics in May 2012 reported that food allergy prevalence was not associated with latitude or geographic region.  Surprisingly, urban residence was most associated with increased odds of having a food allergy and a history of life-threatening allergic reactions to food.

Though it is not completely understood why, infants are at increased risk of developing food allergies. According to specialists at the University of California San Francisco’s Benioff Children’s Hospital, this could be due, in part, to the fact that they are introduced to a large number of new foods, with an abundance of new and potentially allergenic food proteins, in their first few years of life. Another potential factor for increased risk of food allergy in infants is the fact that their digestive processes are not fully developed. This can potentially allow some proteins to escape the digestive tract and enter the bloodstream where they are flagged by the immune system as a threat. Most food allergies developed in infancy do not persist into adulthood.

The Facts

Though research into food allergies is ongoing, they are not completely understood, and the problem is not likely to be resolved quickly. According to the Food Allergy and Anaphylaxis Network, an estimated 15 million Americans suffer from food allergies. Approximately 5 percent of American children under the age of five and 4 percent of people five years and older have to meticulously manage their food intake for fear of eating something that might cause them to break out in hives, or worse, experience anaphylaxis. Evidence suggests that the number of people with food allergies, as well as the number of people suffering anaphylaxis as a result, is increasing every year with no real solution in sight.

There is no cure for food allergies, so it is imperative that if you suspect a food allergy, you get a medical diagnosis identifying the precise cause of the allergy.  This is essential to being able to manage the problem successfully.

What we Recommend

If you suspect that you or a family member may have a food allergy, it is important that you consult your doctor. The only way to determine for certain if you have a potentially life-threatening allergy is to undergo testing.

A medical diagnosis will help distinguish between a potential food allergy and a case of food intolerance, which does not involve the immune system.  Foods often associated with food intolerance include milk, wine, chocolate, some sulfites and MSG. Reactions and discomfort associated with food intolerance generally tend to come on slowly instead of suddenly.

A key part of a successful strategy for avoiding allergic reactions is knowing your precise allergy and avoiding the food as much as possible.  Your doctor can provide you with a range of useful options in dealing with your particular allergy in everyday life.

Part 2 of this series, Food Allergy Basics – Part 2: The Usual Suspects, will examine in greater detail the eight foods that account for the majority of food allergies.