What the 9 Major Food Allergens Are, and Where They're Lurking

Eggs, milk and wheat are common ingredients in baked goods and pose a threat to a chunk of the population.
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Food allergies can be life-threatening for people affected by them, and avoiding the allergens can seem like a full-time job.

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Up to 32 million people in the United States have food allergies, according to the Allergy and Asthma Foundation of America. While it's common for children to develop food allergies and then outgrow them, this isn't always the case.

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One in four adults with a food allergy develops the allergy as an adult, per a November 2018 paper published in the Annals of Allergy, Asthma, and Immunology.

So what is a food allergy, exactly? A food allergy occurs when the body treats a protein in a specific food as an invader. A chemical chain reaction then happens, causing symptoms as mild as a runny nose to severe life-threatening symptoms like anaphylaxis (a reaction that leads to rapid pulse, tightening of the airways and shock), according to the U.K. National Health Service.

While any food could potentially cause an allergic reaction, these nine foods are the most common food allergens.

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1. Milk

Most infants and children will outgrow their milk allergies.
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A cow's milk allergy is a common food allergy that affects children and adults. It's estimated that 2.5 percent of children under 3 in the U.S. have a milk allergy, according to Food Allergy Research & Education (FARE). While most kids outgrow this allergy, many do not.

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A milk allergy occurs when your body identifies one, or both, of the proteins in milk as harmful. Casein and whey are the two proteins in milk that may cause this reaction.

Symptoms of a milk allergy could include hives, wheezing, itching or swelling of the lips and tongue, shortness of breath or vomiting, according to the Mayo Clinic. Milk is the most common cause of food protein-induced enterocolitis syndrome (FPIES). The Mayo Clinic describes FPIES as a reaction that includes vomiting and diarrhea which occurs hours after exposure, not minutes, like many other allergy symptoms.

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"Whey, a milk protein, is often missed on the label of products like protein powders and meal replacements, so be sure to read the 'contains' statement on labels," says Amanda Liptak, RDN, a registered dietitian at Nutrient Rich Life.

Many family favorites contain milk in the form of cheese, sour cream, ricotta cheese and whipping cream. To enjoy some traditionally dairy-heavy foods, Liptak suggests "swapping out the ricotta cheese filling in Italian-inspired dishes like lasagna for tofu, which easily takes on the shape and flavor that it's mixed with."

Foods That Contain Milk

  • Cheese (including ricotta and cream cheese)
  • Sour cream
  • Whey or casein-based protein powders
  • Ice cream
  • Yogurt
  • Butter
  • Cereals, baked goods or candies made with butter, milk, or milk powder

2. Egg

Eggs are the second most common food allergy.
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"Eggs are the second most common food allergy aside from milk," Liptak says. While egg allergies are most common in children, they can stick around into adulthood. FARE estimates that 71 percent of children outgrow their egg allergy by age 6.

An allergic reaction to eggs is caused by an overreaction of the immune system when it comes in contact with the proteins in the egg white, yolk, or both.

The most common reaction to egg allergies is skin-related such as hives, per the Mayo Clinic. They can also include digestive symptoms, congestion and even severe reactions such as anaphylaxis.

Eggs are a staple when it comes to home baking, but there are other egg-free binders you can use for muffins, cookies, and more. For an easy replacement when baking at home, "use 1 tablespoon ground flaxseed mixed with 3 tablespoons warm water. Allow the mixture to thicken for a few minutes before using it in a recipe to replace one egg," Liptak says.

While there are several different names that egg can be referred to on a label, the U.S. federal law requires egg to be identified in plain language in the "contains" statement on a food package.

Foods That Contain Egg

  • Mayonnaise
  • Baked goods
  • Hollandaise
  • Custard
  • Crackers
  • Salad dressing
  • Pretzels
  • Marshmallows
  • Processed meats
  • Meringue

3. Soy

Up to 88 percent of people who are allergic to soy are also allergic to peanuts.
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Soy allergies are most common in infants and children, with 0.4 percent of infants in the U.S. having a soy allergy, according to FARE. Soybeans are a part of the legume family, along with beans, peas, lentils and peanuts. While someone who is allergic to peanuts is not likely to also be sensitive to soy, up to 88 percent of people who have soy allergies are also allergic to peanuts, per FARE.

While anaphylaxis is a severe symptom for some people with a soy allergy, for most people the symptoms are less severe. The Mayo Clinic states the most common symptoms of a soy allergy are itching or swelling of the face, lips and mouth, hives, flushed skin and stomach pain.

While staying away from soy products like soy milk, edamame or tofu is straightforward, many other foods have soy as an added ingredient. You may need to be cautious of foods containing "vegetable gums," "hydrolyzed vegetable protein" or "monosodium glutamate" on the ingredient label as they are sometimes sourced from soy.

Foods That Contain Soy

  • Soy milk
  • Tofu
  • Miso
  • Soy sauce
  • Tempeh
  • Tamari
  • Edamame
  • Textured vegetable protein
  • Grains or cereals prepared with soy
  • Cookies, crackers, dairy products or processed meats made with soy

4. Fish

Up to 40 percent of people with a fish allergy get their first reaction as an adult.
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A person allergic to fish may react to any finned fish, including salmon, cod, tuna, catfish and more. Fish is one of the major food allergens with 1 percent of the U.S. population having an allergy, according to FARE. Many allergies start in childhood, but with fish, 40 percent of people experience their first reaction as an adult.

A specific protein in fish, parvalbumin, is the main trigger for a reaction, per the European Centre for Allergy Research Foundation (ECARF).

While most people have to eat fish for a reaction to occur, some can react by coming into contact with steam or dust particles from fish in the air. Symptoms can range from anaphylaxis to itching of the mouth, diarrhea, congestion and shortness of breath or skin rash.

Foods That Contain Fish

  • Fish sauce
  • Fish oil
  • Salad dressings
  • Steak sauce
  • Fish stock
  • Imitation crab

5. Shellfish

Shellfish allergies affect 2 percent of the world population.
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Shellfish allergies affect 2 percent of the world population. Unlike most other food allergies, those who developed a shellfish allergy are unlikely to outgrow it, per November 2016 research published in Allergo Journal International.

Sixty percent of people experience their first allergic reaction to shellfish as adults, according to the Cleveland Clinic. While this isn't typical for most food allergies, many people don't try shellfish as children, which is most likely the reason for the onset later in life.

Within minutes of exposure, a person with a shellfish allergy may experience itching or swelling of the mouth, throat or face, hives, dizziness, wheezing, nausea or diarrhea. Anaphylaxis is a common life-threatening symptom of a shellfish allergy.

Types of Shellfish

  • Squid
  • Snails
  • Clams
  • Oysters
  • Crab
  • Lobster
  • Crayfish
  • Shrimp
  • Prawns
  • Krill

Foods That Contain Shellfish

  • Fish or seafood stock
  • Fish Flavoring

6. Peanuts

Within minutes, someone with a peanut allergy can develop a severe reaction called anaphylaxis.
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Peanut allergy is one of the most common food allergies in children and adults. While some infants and children outgrow peanut allergies and can enjoy them as adults, many do not. Only 20 percent of children outgrew the allergy in a May 2015 study in the Journal of Allergy and Clinical Immunology.

Within minutes of exposure, anaphylaxis can occur in those with peanut allergies. Other, less severe symptoms include hives, itching, tingling, or swelling of the mouth, tongue, and throat, diarrhea or vomiting, runny nose or shortness of breath.

Many families who have a member with peanut allergies include replacements to keep the risk of a reaction as low as possible. Using almond butter or sunflower seed butter instead of peanut butter for baking, sandwiches and snacks is a great substitute.

Foods That Contain Peanuts

  • Peanut butter
  • Beer nuts
  • Mixed nuts
  • Candies or cookies
  • Granola or trail mix containing peanuts
  • Any food containing peanut oil

7. Tree Nuts

There are 19 different nuts that the FDA requires to be identified as "tree nuts" on food labels.
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Tree nuts contain different proteins than peanuts or seeds and fall into their own allergen category. There are 18 different types of tree nuts and 50 percent of children allergic to one type of tree nut will have an allergy to another, per FARE.

Even though the proteins in tree nuts are different than peanuts, 25 to 40 percent of people allergic to peanuts will also have an allergy to at least one tree nut, according to the American College of Allergy, Asthma, and Immunology. Because of the high potential of cross-contamination, many choose to avoid any products containing peanuts or tree nuts if they have an allergy to either.

For some, even a small amount of tree nuts can cause anaphylaxis. Other symptoms can include diarrhea, vomiting, itchy eyes, mouth or throat, difficulty swallowing, shortness of breath or runny nose.

Types of Tree Nuts

There are 18 tree nuts (plus coconut) that the Food and Drug Administration (FDA) requires to be acknowledged on food labels:

  • Almonds
  • Beechnut
  • Brazil nuts
  • Butternut
  • Cashews
  • Chestnuts
  • Chinquapin
  • Coconut
  • Hazelnut
  • Ginko nut
  • Hickory nut
  • Lichee nut
  • Macadamia nut
  • Pecan
  • Pine nut
  • Pili nut
  • Pistachio
  • Shea nut
  • Walnut

Foods That Contain Tree Nuts

  • Pesto
  • Nut milks
  • Pralines
  • Nut paste
  • Nut butter
  • Nut meals or flours

8. Wheat

Two-thirds of children with a wheat allergy will outgrow it in adulthood.
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Wheat allergies affect 1 percent of U.S. children, according to FARE, but two-thirds of those outgrow the allergy before adulthood.

Wheat allergies are sometimes confused with celiac disease, but the causes of the two are completely different. A wheat allergy occurs when a person's immune system has an IgE-mediated response and results in allergic symptoms similar to the other allergen responses.

Celiac disease is an autoimmune disease where antibodies are produced when the body comes into contact with gluten, and damage occurs on a cellular level in the small intestine. Someone with a wheat allergy may experience itching and swelling of the mouth or throat, nasal congestion, hives or skin rash, diarrhea cramps or even anaphylaxis.

Wheat is one of the most commonly used grains in the United States. It can be tricky, but possible, to find substitutes.

"One of the things my clients say they miss the most when first diagnosed with wheat allergy is pizza," says Liptak. "When they try cauliflower crust though, they are pleasantly surprised by the crispness and depth of flavor cauliflower has to offer! Many clients enjoy making their own cauliflower crust at home by combining one head of cauliflower, 2 eggs, 1 cup of ground almonds and a pinch of salt."

Foods That Contain Wheat

  • Breadcrumbs
  • Couscous
  • Pizza
  • Pasta
  • Seitan
  • Farro
  • Einkorn
  • Spelt
  • Whole-wheat berries
  • Soy sauce
  • Cereals
  • Baked goods with wheat flour

9. Sesame

By 2023, sesame will be identified on food labels as a potential allergen.
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Sesame is not considered one of the Big 8 allergens identified by the FDA as the group of allergens that make up 90 percent of all food allergies but will soon be treated the same. In 2023, sesame will have the same label requirements as the other eight allergens, according to FARE, as 0.23 percent of children and adults have a sesame allergy.

An allergic reaction to sesame ranges from severe, such as anaphylaxis, to mild skin rashes or stomach upset.

Many Asian, Thai and Mediterranian dishes may contain sesame. Because sesame is not currently required to be stated on food labels, it may be listed as only "spice blend" in an ingredient list. This can make it difficult to identify the presence of sesame in some foods.

Foods That Contain Sesame

  • Hamburger buns
  • Hummus
  • Falafel
  • Sushi
  • Tahini
  • Processed meats
  • Crackers
  • Dressings

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