Food Allergy Causes

Written by the Healthline Editorial Team | Published on July 21, 2014
Medically Reviewed by George Krucik, MD, MBA on July 21, 2014

What Causes Food Allergies?

A food allergy is caused by an inappropriate immune system response to a specific food or substance in a food. Your immune system mistakes a food for a harmful substance, and creates immunoglobulin E (IgE) antibodies to fight it. Then, the next time you eat that food—even the tiniest bit of it—the IgE antibodies sense it and cause your immune system to release chemicals to fight it off. These chemicals cause the symptoms of an allergic reaction.

According to the U.S. Food and Drug Administration (FDA), eight kinds of food cause 90 percent of food allergies. Luckily, the Food Allergen Labeling and Consumer Protection Act of 2004, which took effect January 1, 2006, requires food manufacturers to disclose in plain language whether packaged products contain any of these eight types of food (or proteins that came from these foods):

  • milk
  • eggs
  • peanuts
  • wheat
  • soy
  • fish
  • shellfish
  • tree nuts

This labeling requirement does not apply to meat, poultry, and egg products, which are regulated by the United States Department of Agriculture’s (USDA) Food Safety and Inspection Service (USDA).

Factors That Increase Your Risk of Having a Food Allergy

Certain factors put you at greater risk for having a food allergy.  


According to the Mayo Clinic, food allergies are most common in toddlers and infants. Allergies to milk, soy, wheat, and eggs may decrease in impact over time. Allergies to nuts and shellfish are more likely to last a lifetime.

Family History

If asthma, eczema, hives, or hay fever is part of your family’s background, you are more likely to have a food allergy.

Other Allergies

If you're already allergic to one food or already have another type of allergy, you have a greater risk of developing a food allergy.

Asthma and Eczema

Asthma and food allergies often coexist. Asthma can also make food allergy symptoms more severe.

A Past Food Allergy

Although a food allergy that develops during childhood may mitigate as you grow older, there is still a chance the allergy may return later in life.

Most Common Food Allergens


Milk allergies are much more common among children than adults; they are especially common among very young children. According to the Food Allergy & Anaphylaxis Network (FAAN), milk allergy is the most common childhood food allergy, affecting two-and-a-half percent of children under the age of three..

Two types of protein in milk can cause an allergic reaction: casein and whey, with whey being the culprit in the majority of cases.


As with milk, egg allergies are much more common among children than adults. According to FAAN, at least one-and-a-half percent of children have this allergy. A number of proteins in both the yolks and whites of eggs can cause allergies. However, according to the Mayo Clinic, allergies to egg whites are more common than allergies to egg yolks. It is important to note that those with severe egg allergies should talk to their doctor before receiving a flu shot, as eggs are used to create the vaccine.


Peanut allergies are more common in children than in adults. About one-and-two-tenths percent of children are allergic to peanuts.

Peanuts are the cause of the most severe food allergy attacks. Therefore, it is essential to get your child checked for a peanut allergy even after the mildest of reactions to peanuts or peanut butter. Even if your child has only had minor reactions, there is a serious risk for severe attacks in the future.

Many food products that don’t contain peanuts are processed in plants with peanuts, and may have some peanut proteins in them. Make sure to read food labels carefully if you or your child has a peanut allergy.


Four classes of wheat proteins can cause allergic reactions: albumin, globulin, gliadin and gluten. Wheat proteins, especially gluten, are used in many types of food, including:

  • bread
  • cake and muffins
  • pasta
  • crackers
  • beer
  • ketchup
  • soy sauce
  • ice cream
  • food starch
  • natural flavorings

Some people have an exercise-related allergy to wheat. These individuals have severe symptoms that only appear if they exercise within a few hours after eating wheat. According to the Mayo Clinic, some individuals with this type also experience these symptoms if they take aspirin or diclofenac (Cataflam, Voltaren). Unfortunately, these people often experience anaphylaxis if their symptoms are triggered.

Celiac disease is sometimes incorrectly called a gluten allergy, when it is really a digestive disorder. An individual can have both a wheat allergy and celiac disease, however.

Baker’s asthma occurs when a person has difficulty breathing after inhaling wheat or other types of flours. However, these individuals can often eat cooked wheat products without a problem.


Soy allergies are also more common among children than adults. According to the Food Allergy Initiative (FAI), most children will react less intensely to soy by the time they are three. Most of the time, allergic reactions to soy are mild.

Because soy is used in many products where its use may not be obvious, it is important to read all food labels if you have a soy allergy. When reading labels, look for the following words: soy, soya, soybeans, glycine max, and edamame.


Although a person with a fish allergy may be allergic to only one species of fish, it is generally recommended that he or she avoid all fish to be on the safe side. Unlike many other food allergies, fish allergies tend to last a person’s whole life. This is one of the most common food allergies in adults.

Fish is often used in food products where it may not be expected, so always read food labels if you have a fish allergy.


All sorts of shellfish can cause allergic reactions: crustaceans (e.g., crabs, lobster, shrimp, prawns),and mollusks (e.g., clams, mussels, oysters, squid, and octopus). Some people are only allergic to one kind of shellfish; others must avoid all types. Shellfish allergies are more common among adults than children.

According to the American College of Asthma, Allergy, & Immunology (ACAAI), along with peanuts and tree nuts, shellfish allergies are more likely to cause anaphylaxis symptoms.

Tree Nuts

Tree nuts that may cause an allergic reaction include almonds, pecans, cashews, pistachios and walnuts. As with shellfish, some people are allergic to only one type of nut, while others have reactions to all. 

According to ACAAI, tree nuts, along with peanuts and shellfish, are more likely to cause anaphylaxis symptoms.

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