Understanding Food Allergies

by Natalie Digate Muth, MD, MPH, RD on Sep 01, 2006

How to help clients recognize and prevent allergic reactions to some of the most common food culprits that affect kids and adults.

The health benefits of nuts like walnuts, pecans and almonds have been widely touted of late. Recent studies confirm that the advantages of eating nuts in moderation can range from building immunity to preventing heart disease. But for the millions of Americans with food allergies, the advice to eat nuts could be hazardous to their health. For these individuals, nuts—or a variety of other food allergens, such as shellfish and milk—could prove deadly.

Did you know that approximately 200 Americans die each year from food-induced anaphylaxis, a severe and potentially fatal systemic allergic response (Sampson 2002)? Some 30,000 adults and children end up in U.S emergency departments suffering from an anaphylactic reaction to food (Food Allergy & Anaphylaxis Network [FAAN] 2006a). And you don’t have to pig out to be a victim of a food allergy. Sometimes, exposure to even a miniscule amount of an allergen can be extremely harmful. All it took was a kiss from a boyfriend who had eaten peanut butter to cause one Canadian teen to succumb to a fatal allergic reaction late last year (The Canadian Press 2005).

Allergy Nation

For reasons not yet fully understood, food allergies appear to be on the rise. In the United States, up to 8% of children and 2% of adults now suffer from them (U.S. Department of Health and Human Services [DHHS] 2004). While much more common in children than adults (see “Food Allergies in Children & Teens” on page 82), allergies affect people of all ages and ethnicities.

Chances are, at some point in your fitness career, you will encounter a client, friend or family member who is allergic to a particular food. When that happens, it will be important to recognize the most common food allergies, what causes them, how to identify them, and what people with allergies (and their parents, in the case of children) can do to avoid experiencing their harmful symptoms.

Understanding Food Allergies

The 8 most common food allergens, which account for 90% of all allergic reactions, are milk, eggs, peanuts, tree nuts (such as almonds, cashews and walnuts), shellfish, fish, soy and wheat (Mayo Clinic 2006).

With repeat exposure to the food, the antibody responds by binding to the allergen. This sets in motion a series of immunologic events, including the release of the hormone called histamine. Histamine is responsible for many food allergy symptoms, which include redness, swelling, itching, gastrointestinal symptoms and hypotension.

Once the body creates an antibody to a food, an immune response ensues every time that food is eaten. In rare but deadly cases, the heart rate drops, the breathing tubes narrow and the tongue swells, making breathing and adequate oxygenation to the body’s cells a struggle. The harmful response can occur from minutes to an hour after the food is eaten (DHHS 2004).

Fishing for Red Herrings

When symptoms first appear, it’s important to differentiate between a real food allergy and another potential cause. Often, the cause of the ailment is something else, such as food poisoning, a nonfood allergen (such as pollen, dust or dander) or—most commonly—a food intolerance.

While food allergies and food intolerances both result from the body’s inability to handle specific foods, the mechanisms at play that cause the symptoms are quite different. A food intolerance results from a deficiency in an enzyme needed to break down a food. For example, lactose intolerance results from a deficiency in the enzyme lactase, necessary to digest the sugar. Undigested lactose can cause gastrointestinal symptoms, such as abdominal pain, bloating and diarrhea. Unlike with a food allergy, the immune system plays no role in the dysfunction (DHHS 2004), and the uncomfortable symptoms are not life threatening.

Proper Handling of Clients With Food Allergies

Clearly, rapid treatment is critical for any client showing the symptoms of a severe allergic reaction, such as dizziness, wheezing, falling blood pressure or difficulty breathing. Emergency medical services should be contacted to transport the client to the hospital (in mild cases, you can drive the person to a local emergency room). Medical treatment may involve injectable epinephrine, antihistamines and other emergency measures (American Academy of Allergy, Asthma & Immunology [AAAI] 2006). These medicines reverse the allergic response by restoring blood pressure, blocking further production of histamine and countering the harmful effects induced by the allergen.

After treatment of acute symptoms of an allergic reaction, the client will need to be referred to an allergist, who will try to identify the food culprit. This step can be either a simple process or an arduous, time-consuming journey. The physician’s first objective will be to get a complete history of the reaction, including onset and duration, symptoms, seasonality, suspect foods, how the foods were prepared and any other information the patient can provide. A complete physical exam will follow, to gather as much information about the reaction as possible. In most cases, this comprehensive assessment will reveal a few suspect foods.

Usually the next step for the client (but not for one who has had a severe reaction!) is to keep a food diary, to document all foods eaten and any allergic reactions. If a potential allergen is noted, it is then removed from the diet and the client continues to keep the food diary. If the symptoms disappear after a suspect food is eliminated from the diet, the diagnosis is fairly obvious, and the patient should strive to avoid the offender.

If, however, the diagnosis remains uncertain, the allergist can do a scratch skin test. With this test, a small amount of the food is placed on the skin of the lower arm, which is then checked for redness and swelling. If the test is positive for a particular food, the diagnosis is confirmed. Another test option is the gold standard for food allergy diagnosis: the double-blind food challenge. The patient swallows a series of capsules that contain different common food allergens and is then watched to see if symptoms occur. Neither the patient nor the physician knows which food is in which capsule (the capsules are prepared by a third party). Unfortunately, this test is time-consuming and impractical for many allergens and, as such, is rarely performed.

Of course, all these tests could be deadly for people with severe allergic reactions. For these individuals, diagnosis is made with a blood test that measures the presence of a food-specific antibody (DHHS 2004).

Preventing Future Reactions to Food

Once a diagnosis is confirmed, there is only one way to prevent a future attack: The client must avoid the food. This is no simple task, considering the widespread use of many of the most common food allergens; peanuts, for example, are a common food additive.

To help ease the burden, the U.S. Food and Drug Administration (FDA) this year implemented a new law requiring food-manufacturing companies to list on product labels any of the 8 most common allergens (see sidebar on page 81) included in food items. While this certainly will help, people with food allergies—and especially parents of kids who are vulnerable—must still be vigilant. And those with severe allergic reactions should always carry an epinephrine pen (for injecting epinephrine, which is used to treat the reactions) and wear a medical-alert bracelet noting the specific allergy.

What About Exercise?

Many myths surround food allergies. For example, it’s commonly said that food allergies cause or exacerbate migraine headaches, arthritis, fatigue and childhood hyperactivity. But there is no credible scientific evidence to support those claims (DHHS 2004). However, one “myth” is actually true: In certain situations, exercise can transform an otherwise benign food into a potent allergen. This is what’s known as an exercise-induced food allergy.

According to the National Institute of Allergy and Infectious Disease (NIAID), “People who have this reaction only experience it after eating a specific food before exercising. As exercise increases and body temperature rises, itching and light-headedness start and allergic reactions, such as hives, may appear and even anaphylaxis may develop” (DHHS 2004).

The NIAID says the cure for this is “simple”: Until the culprit food is identified, people with a history of exercise-induced allergies should avoid eating for a couple of hours before exercising.

Where You Can Help

As a fitness professional, you regularly update your CPR and first-aid certifications so that you’ll be prepared to help clients in case of an emergency. While food allergy management probably has not been on your radar, it should be! This is especially true if you work with children and teens or if you train anyone susceptible to an exercise-induced or typical food allergy. Before you know it, you may be faced with the task of recognizing and responding to anaphylaxis or some other severe allergic reaction in a client. If you are prepared and think fast, you could save someone’s life.

the 8 most common food culprits

Accounting for a whopping 90% of all allergic reactions, here are the 8 foods that most commonly cause symptoms ranging from itching to life-threatening anaphylactic shock:

  • milk
  • eggs
  • peanuts
  • tree nuts (e.g., almonds, cashews and walnuts)
  • shellfish
  • fish
  • soy
  • wheat

food allergies in children & teensPeanut butter and jelly sandwiches and chocolate milk are childhood favorites. But for some 2 million American children with food allergies, these snacks top the list of forbidden foods (KidsHealth 2005). Just one taste of these foods can wreak havoc on a child’s immune system, which mistakenly identifies them as unwanted invaders.

While many kids outgrow their allergies by adulthood, managing an allergy during childhood and adolescence can be a full-time operation—for the kids themselves and for their worried parents. And recent research suggests that while parents may be vigilant with younger children—making sure they carefully read labels, carry an epinephrine pen in case of emergency and strictly avoid allergens—teens become more willing to take risks as they gain independence. A survey of 174 teenagers found that while 74% said they always carried their emergency epinephrine, the respondents also reported being more likely to leave the life-saver at home during sports, when attending a school dance or when wearing tight clothes. And whereas 75% said they always read nutrition labels to avoid allergens (FAAN 2006b), a whopping 42% said they would eat a food that “may contain” a food allergen (FAAN2006b).

The Food Allergy & Anaphylaxis Network (FAAN) offers the following tips on helping a teen manage a food allergy:

  • Communicate openly, being careful not to embarrass, ridicule or yell. Share concerns and fears, and provide positive reinforcement and encouragement whenever possible.
  • Discuss the seriousness of food allergies and the danger of risk taking.
  • Outline specific responsibilities (reading labels, always carrying epinephrine, etc.) and the consequences of not following them.
  • Try to let go! While it is tempting to try to control teens, the better tack is to empower them to manage their allergies and to be careful not to take over or micromanage (FAAN 2006c).
    Additional Allergy Resources

    For a look at the entire online National Institute of Allergy and Infectious Disease health info pamphlet Food Allergy: An Overview, contact www.niaid.nih.gov/publications/pdf/ foodallergy.pdf.


American Academy of Allergy, Asthma & Immunology (AAAID). 2006. Tips to remember: Food allergy. www.aaaai.org/patients/publicedmat/tips/food

allergy.stm; retrieved May 16, 2006.

The Canadian Press. 2005. Girl with peanut allergy dies after kiss. Toronto Sun (November 25). www.toronto

sun.com/News/2005/11/25/pf-1323368.html; retrieved May 16, 2006.

Food Allergy & Anaphylaxis Network (FAAN). 2006a. Press release: Avoiding food allergens is a formidable task. www.foodallergy.org/press_releases/avoiding

foodallergens.html; retrieved May 16, 2006.

Food Allergy & Anaphylaxis Network (FAAN). 2006b. FAAN to discuss risk-taking and coping strategies of teens with food allergies at the AAAAI annual conference. Medicalnewstoday.com; retrieved May 17, 2006.

Food Allergy & Anaphylaxis Network (FAAN). 2006c. Talking to your teen about food allergy. www.food

allergy.org/downloads/teenbrochure.pdf; retrieved May 17, 2006.

KidsHealth. 2005. Food allergies. http://kidshealth.org; retrieved May 17, 2006.

Mayo Clinic. 2006. Food allergies: New food-labeling requirements. www.mayoclinic.com/health/food-allergies/AA00057; retrieved May 16, 2006.

Sampson, H. 2002. Peanut allergy. New England Journal of Medicine, 346 (17), 1294–99.

U.S. Department of Health and Human Services (DHHS). 2004. National Institutes of Health, National Institute of Allergy and Infectious Disease: NIH

Publication No. 04–5518. www.niaid.nih.gov/pub

lications/pdf/foodallergy.pdf; retrieved May 16, 2006.

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About the Author

Natalie Digate Muth, MD, MPH, RD

Natalie Digate Muth, MD, MPH, RD IDEA Author/Presenter

Natalie Digate Muth, MD, MPH, RD, is a registered dietitian and a recent graduate of the UNC School of Medicine. She has made several appearances as a nutrition expert on CW's San Diego 6, been quo...