Corn Allergy and Following a Corn-Free Diet

Read Labels Carefully for Corn or Corn Products

Shucking corn raising concern about corn allergy and a corn free diet
 Valeriya Tikhonova/Getty Images

Corn allergy isn't as common as some allergic reactions to foods, but when it occurs, can sometimes be severe (anaphylaxis). Symptoms can range from itching, redness, and nasal congestion, to wheezing, throat swelling, and shock. The diagnosis can be challenging and is usually based on history. The only treatment for anaphylaxis is epinephrine injection (EpiPen) making prevention the primary objective. Let's look at what you should know about corn allergy, including foods (from cornstarch to white vinegar) and non-food products (from toothpaste to stamps) that may contain corn, as well as corn-free foods that are usually safe.

Understanding Food Allergies

Food allergies are common, though allergies to foods such as nuts, shellfish, and wheat are better understood. Unlike many of these other allergies, however, current food labeling does not list foods as "corn free" and it's up to individuals to become familiar with the many ingredients and non-food sources containing corn, in order to avoid exposure.

Corn Allergy

Corn is a cereal grain that contains a protein, zein, that is thought to be the culprit in allergic reactions. Not all corn products contain zein, but it can be difficult to know when it is present.

An allergic reaction occurs when the body recognizes this protein as foreign and releases antibodies (IgE) to attack the protein. IgE (immunoglobulin E) then stimulates cells in the immune system to secrete substances such as histamines that are responsible for the symptoms.

Allergic reactions can occur as a result of eating both raw and cooked corn, as well as foods manufactured with corn products, or even surgical gloves or intravenous fluids that contain corn. Those who have corn allergy may also react to corn pollen, grass pollen, and cornstarch (typically with hayfever (allergic rhinitis) and/or asthma).

Signs and Symptoms

Allergic reactions to corn can take different forms. Common symptoms include:

  • Hives
  • Itching, particularly in or around the mouth (oral allergy syndrome) but may be generalized as well
  • Flushing or reddening of the skin
  • Hay fever-like symptoms with sneezing, nasal congestion, or a runny nose
  • Wheezing (asthma)
  • Headaches
  • Abdominal pain
  • Nausea and/or vomiting
  • Diarrhea

Anaphylaxis may also occur and can include symptoms such as:

  • Swelling and/or tightness of the lips, tongue, throat, neck, or face
  • Difficulty breathing
  • Hoarse voice
  • Lightheadedness
  • Rapid heart rate
  • Lethargy, confusion, or loss of consciousness
  • A sense of impending doom

Anaphylaxis is a life-threatening emergency, and immediate medical treatment is needed (you should call 911 immediately if you suspect you or a loved one may be having such a reaction).

Causes/Risk Factors

The exact causes of corn allergy aren't known, but it's thought to be due to a combination of genetic factors, environmental factors, and epigenetic factors (the interaction of genetics and the environment).

People who have asthma, eczema, hives, hayfever, or other food allergies appear to be at greater risk. A family history of these conditions is also associated with a higher risk, particularly when a sibling has a corn allergy.

Incidence

It's uncertain exactly how common corn allergy is, but some researchers believe it's underdiagnosed. A 2016 study in Pakistan, found the rate to be 0.86, or almost 1 percent of the population. In the study, a diagnosis of allergy was confirmed by a food challenge. One study in Honduras of only 50 adults found the prevalence to be 6 percent, but we currently don't have a good estimate about the incidence in the United States. Since corn is present in so many products (found in roughly 75 percent of processed foods), minor symptoms, such as rashes or hay fever symptoms could be easily overlooked as due to something else.

Diagnosis and Testing

Diagnosing food allergies is important, as the results can have a significant impact on what a person eats each and every day. That said, the diagnosis of corn allergy can be challenging. Allergy testing with blood tests and skin tests can be inaccurate, with false positive tests occurring often. (A false positive test is one which says there is a problem when there isn't an allergy present.) People who have an allergy to one cereal grain often have false positive allergy tests to other cereal grains. A false positive, however, does place a person at a higher risk for an allergic reaction to that food and should be considered along with other findings.

A careful history is often the most reliable indicator of a corn allergy, with symptoms of an allergic reaction occurring after eating corn or foods containing corn. The history, however, can be difficult to evaluate for a few reasons. One is that corn is present in a vast number of foods and in different amounts. Another is that the signs and symptoms are non-specific, and may easily be dismissed as a cold virus, a rash due to irritation, or an allergic reaction due to something else.

With mild symptoms, keeping a food diary is often an excellent start. This involves recording foods that are eaten, when they are eaten, and any symptoms you experience. An elimination diet can also be very helpful. With an elimination diet, the foods that are eaten are greatly restricted, and then individual foods are slowly added back in at particular intervals. The diet often requires a commitment of a minimum of 2 weeks and often more to identify potential food allergies. If a corn allergy is suspected, a food challenge (eating corn) may be considered, but should only be done under the guidance of an allergist. Consulting with an allergist who specializes in food allergies early on can be very helpful, and is imperative if you have had any symptoms suggestive of an anaphylactic reaction.

Treatment

For mild allergic reactions, treatment usually consists of managing the symptoms alone until the allergic reaction is done.

For anaphylactic reactions, epinephrine (an EpiPen) is the only treatment available, along with immediate medical care in an emergency room. Anyone who is coping with possible food allergies that could result in a severe allergic reaction should become familiar with first aid for anaphylaxis, and be prescribed, and learn how to use an EpiPen.

Prevention

Certainly, the best way to "treat" corn allergy is to avoid corn in the first place. That said, with the many "hidden" sources of corn in a typical American diet, exposures can and do occur. Below we list both obvious and less obvious sources of corn in a typical diet. Unlike some allergies, such as wheat allergy, foods aren't labeled as "corn free," and avoiding corn requires learning about the many ingredients that may contain corn. Working with a nutritionist or dietician can be very helpful in navigating the vocabulary.

Even when you become familiar with reading ingredients while grocery shopping, it can be challenging when you are asked to eat at the homes of family and friends, out at restaurants, and for children, eating at school. At restaurants, it's a good idea to ask to talk with the chef. This conversation should include not only the ingredients used but how the food is prepared (for example, a corn-free dish may be fried in corn oil).

How to Follow a Corn Free Diet and Lifestyle

Below we list out foods that always or often contain corn, foods that may contain corn (including many items that may be listed in the small print on an ingredient list), and non-food items that may contain corn. These non-food items are equally important to consider, as anaphylactic reactions have occurred due to cornstarch on surgical gloves and even certain intravenous fluids. Following these lists, we list some food items that are generally safe on a corn free diet. Please note that this is not an exhaustive list, and it's highly recommended that you work with both your allergist and a dietician if you have a serious reaction to corn.

Foods That Always or Often Contain Corn

Some foods, such as corn-on-the-cob are easily recognized as corn products. keep in mind that maize, however, is the same as corn. Foods that should be avoided completely on a corn free diet include:

  • Corn syrup, high-fructose corn syrup, corn oil, cornmeal, cornstarch (high fructose corn syrup may appear under ingredients as HFCS)
  • Vegetable oil
  • Maize
  • Popcorn
  • Grits
  • Hominy
  • Corn sugars (dextrose, dextrin, maltodextrin, fructose, Dyno, Cerelose, Puretose, Sweetose, glucose, sorbitol, xylitol, inositol, sodium erythorbate)
  • Margarine
  • Corn chips (tortilla chips, Fritos) and corn fritters
  • Breakfast cereals (such as corn flakes, grits)
  • Corn tortillas

Foods That May Contain Corn Products

Use caution with the following foods, which may include sources of corn from various products, such as cornstarch, corn syrup, and corn/vegetable oils. Keep in mind that many processed foods (roughly 75 percent) contain corn or products made with corn.

  • Vegetable commercial soups, and chili
  • Peanut butter
  • Various meats (cold cuts such as bologna, ham, hot dogs, sausages, bacon)
  • Breaded or fried foods
  • Cheese and cheese spreads
  • Chop suey and chow mein
  • Fish sticks
  • Fried potatoes or fried rice (if corn oil is used)
  • Frozen mixed vegetables and creamed vegetables
  • Canned vegetables
  • Succotash
  • Pork and beans
  • Bread dusted with cornmeal
  • Graham crackers
  • Baking mixes, pancakes (certain mixes), and pancake syrups
  • English muffins
  • Tacos and tamales
  • Polenta
  • Gravy (thickened with cornstarch, for instance)
  • Salad dressings and sauces
  • Canned or frozen fruits sweetened with corn syrup
  • Dates and other fruit confections
  • Ice creams, sherbets
  • Chocolate milk, milkshakes, soy milk, eggnog, yogurt
  • American wines, whiskey, gin, beer, ale
  • Carbonated beverages such as Coca-Cola, 7-Up, and more
  • Lemonade mixes
  • Instant coffees
  • Jams and jellies
  • Candies and chewing gums
  • Marshmallows
  • Ketchup and mustard (prepared)
  • White distilled vinegar
  • Monosodium glutamate
  • Baking powder, powdered sugar, cake yeast, and bleached flour
  • Gelatin capsules
  • Vanilla extract
  • Malt syrup, modified food starch, caramel, cellulose, xantham gum

Food Packaging Materials May Contain Corn

In addition, certain paper containers (boxes, cups, plates, and milk cartons) may contain corn, and the inner surface of plastic food wrappers may be coated with cornstarch.

Non-Food Items That May Contain Corn

  • Adhesives (envelopes, stickers, stamps)
  • Straws
  • Toothpaste
  • Laundry starch
  • Surgical gloves (due to cornstarch)
  • Some medications, vitamins, minerals, and dietary supplements
  • Pet food
  • Some clothing
  • Crayons
  • Dishwasher soap
  • Shampoo
  • Paint
  • Dextrose intravenous solution

Foods That are Corn Free

Sometimes when beginning a corn-free diet it's easier to look at foods that don't contain corn. These include:

  • Eggs
  • Natural, fresh, non-processed meats and wild-caught fish (those who are very sensitive may want to choose grass-fed beef)
  • Fresh and frozen fruits and vegetables (but read labels with frozen, mixed vegetables), 100 percent fruit juices
  • Oats, wheat, quinoa, lentils, rye
  • Beans
  • Rice
  • Non-flavored milk

Health food stores may also have corn-free products such as corn-free condiments and much more.

A Word From Verywell

Following a corn-free diet can be challenging, especially when it comes to "hidden corn" in some food products or even packaging. In addition to the strict avoidance of any and all of the above foods, it is important to have an Epi-pen available for emergency use at all times in case an accidental ingestion should occur.

The organization Food Allergy Research and Education has many valuable tips for those who are learning how to face life with food allergies, including information on how to prepare for and manage severe reactions.

A Medic-Alert bracelet may be useful in severe forms of food allergy, so that emergency personnel can be aware of your medical condition if you are unable to communicate.

While corn allergy can be limiting and frustrating, there is a silver lining. Many of the foods to avoid on a corn free diet, such as most processed foods, high-carb, and nutrient-poor foods, should be minimized in a healthy diet, and many corn free options are ideal healthy options.

Sources:

American College of Allergy, Asthma, and Immunology. Corn Allergy.

Gonzales-Gonzalez, V., Diaz, A., Fernandez, K., and M. Rivera. Prevalence of Food Allergens Sensitization and Food Allergies in a Group of Allergic Honduran Children. Allergy, Asthma, and Clinical Immunology. 2018. 14(1):23.

Sicherer, S., and H. Sampson. Food Allergy: A Review and Update on Epidemiology, Pathogenesis, Prevention, and Management. Journal of Allergy and Clinical Immunology. 2018. 141(1):41-58.

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