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Food Sensitivities, Allergies, and Intolerances: Separating Fact from Fiction

Food Insight
July/August 2003

In this age of increased attention to nutrition and health, food sensitivities of all types have come to the forefront of the public consciousness in the last few years. This focus has resulted in a number of ideas about how best to address the problem of food sensitivities and allergens and has raised public awareness. Increased research, expanded consumer educational efforts, and food industry initiatives in the areas of processing and labeling have brought significant benefit to people who have food sensitivities.

Unfortunately, for those who suffer from true food allergies, the increased attention to the topic has come at a price. Misinformation about food sensitivities has become abundant on the Web and in the media, and the hype surrounding the issue has elevated food sensitivity into the "trendy" category of human ailments. Yet, true food allergies are not just a playgroup or cocktail party conversation topic—they can be very dangerous, so it is important that they be taken seriously. Here's what you need to know about food sensitivities, allergies, and intolerances and where to go for help.

Types of Food Sensitivities

"There are two types of sensitivities to foods: those that involve the immune system (immunological) and those that don't (non-immunological)," explains Susan Hefle, PhD, co-director of the University of Nebraska Food Allergy Research & Resource Program in Lincoln. "Food intolerances are abnormal reactions to food or food components that do not involve the immune system, while food allergies are abnormal reactions that do involve the immune system," says Hefle.

Food Intolerance:

Food intolerances are the most common types of food sensitivities. They are also generally less severe, more short-lived and more localized than immunological reactions. Within the category of food intolerances there are a few sub-types of intolerances including:

  • Metabolic food disorder: A metabolic food disorder occurs when a person is genetically unable to properly or fully metabolize a food component.


  • Lactose intolerance (inability to metabolize the milk sugar, lactose).
  • Favism (genetic deficiency enhances the sensitivity to a chemical in fava beans).
  • Food idiosyncrasy: Food idiosyncrasy is an abnormal response to a food or food component, but the mechanism for the response is unknown. The symptoms can either resemble those of an allergy and can be either severe or very mild. Some food idiosyncrasies have been scientifically proven, but others have been disproved, such as connections between food colors and hyperactivity.

Example: Sulfite-induced asthma (the food ingredient sulfite, which either is added to food or is naturally occurring in foods, causes asthmatic reactions in 1.7 percent of all asthmatics, or 150,000 Americans). Sulfite-induced asthma has been documented by the research community.

  • Anaphylactoid response: An anaphylactoid response is a type of reaction that elicits the same release of histamine that a true food allergy does, but it does not involve the immune system. The specific substance that causes this reaction has not yet been identified. The response is not the same as anaphylaxis or anaphylactic shock, the rare but life-threatening response to a food allergen.

Example: Strawberry sensitivity

Food Allergy:

While more rare than food intolerances, food allergies are much more severe—and are even potentially fatal. Basically, there are two types of food allergies:

  • Celiac disease: Celiac disease is an inherited condition that affects approximately 1 of every 3,000 Americans, and is due to an unknown genetic defect. People with celiac disease cannot tolerate gluten, a protein found in some grains, such as wheat, rye, spelt, and barley. These grains and products made from them must be avoided to prevent the gastrointestinal symptoms of celiac disease.
  • True food allergy: True food allergy occurs when a susceptible person is exposed to a specific protein component of a food. The body mistakes the protein (the allergen) as a threat producing an antibody to it. With repeated exposures to the offending food, the body becomes primed to release histamine and other powerful biochemicals in response to the allergenic food. It is these chemicals that cause the allergy symptoms. True food allergies are not all that common: and affect less than 2 percent of adults, 4 to 8 percent of young children and infants. The most common causes of food allergy are listed in Table 1 shown on page 4.

Food Sensitivity Symptoms

The symptoms of a food intolerance may be similar to those of a true food allergy. This often leads to confusion, causing people to think that they suffer from a food "allergy" when, in fact, the problem may not be that serious. Table 2, shown on page 4, which lists common symptoms of both true food allergies and food intolerances, should help clarify things.

When Allergy Symptoms Progress to Anaphylaxis

Anaphylaxis is a rare, potentially fatal response to a food allergy. The reaction is characterized by a quick progression through a number of different symptoms instead of the one or two typically seen with food allergies. For example, the reaction may progress quickly from the mild symptom stage, in which the individual experiences an itchy tongue and palate, to a stage of throat tightening and wheezing, and finally to the life-threatening stage of shock and cardiac arrest. Death can sometimes occur before the individual can self-administer life-saving medication (epinephrine). These fatal situations usually occur when the person is dining away from home and inadvertently consumes the offending food, fails to recognize the symptoms quickly, and delays administering epinephrine. According to Hefle, "Although very serious, anaphylaxis is also not a typical food allergy response; it's seen pretty infrequently."

What to Do If You Think You Have a Food Sensitivity

If you have noticed that you routinely experience adverse symptoms after eating a certain food or foods, the first step you may want to take is to keep a log of the experiences. Jot down the date, what food or foods you ate, how they were prepared (if you know), when the symptoms appeared (how long after you ate the food), and exactly what the symptoms were.

Second, make an appointment with your physician and bring the log along. While the log is helpful, it is by no means the only tool that your physician or allergist will use to make a diagnosis. Blood tests, skin tests, and even food challenges may be used to arrive at a diagnosis. Nevertheless, take your log with you when you visit your physician, and if you don't believe the problem has been sufficiently resolved, seek the opinion of a board-certified food allergist.

Finally, do not attempt self-experimentation as a means of diagnosis. Not only can it be dangerous (allergy symptoms can worsen after each exposure), but you'll likely misdiagnose the condition. This can lead to unnecessary worry and hardship, not to mention the nutritional problems that may occur with unwarranted dietary restrictions. So what is the best plan? "Be an informed, helpful patient, but leave the diagnosing to the professionals," advises Hefle. "Your health is just too important."

Table 1. Most Common Causes of True Food Allergy

Infants: cow's milk, eggs, peanuts, tree nuts (chestnuts, walnuts, hazelnuts, Brazil nut, pecans, pine nuts, and cashews), soybeans, wheat

Adults: peanuts, crustacea (shrimp, crab, lobster, crawfish), tree nuts, and fish

Table 2. Food Sensitivity Symptoms

True Food Allergy Symptoms

Someone with a food allergy usually suffers from just a few of the symptoms listed below, not all of them. The onset may occur immediately or within an hour of ingesting the allergenic food. The symptoms fall into five categories:


angioedema (swelling), urticaria (hives), eczema/atopic dermatitis (skin rash)

Gastrointestinal abdominal cramps, diarrhea, nausea, vomiting
Respiratory rhinitis (runny nose), asthma (difficulty breathing), laryngeal edema (constriction of throat)
Oral allergy syndrome mouth, palate, and tongue itching, edema, urticaria (urticaria is associated with fresh fruits and vegetables but rarely occurs during systemic reactions)
Systemic  anaphylactic shock (severe generalized shock)

Food Intolerance Symptoms

Someone with a food intolerance will experience mild, transient symptoms that do not involve the immune system. The onset is between 30 minutes and several hours after consumption of the offending food or beverages.

Gastrointestinal abdominal cramps, diarrhea, nausea
Metabolic hemolytic anemia (in severe cases jaundice and renal failure)

For More Information On Food Allergies and Intolerances

American Academy of Allergy, Asthma and Immunology

American Dietetic Association

Food Allergy and Anaphylaxis Network

International Food Information Council Foundation