Food Allergy

Food allergy is part of a larger group of adverse reactions to food. Food allergy is caused by an immune response that occurs after exposure to a specific food. When exposed, the immune system overreacts by producing antibodies called Immunoglobulin E (IgE) which ultimately cause an allergic reaction. An IgE-mediated immune reaction and is not the same as a food intolerance or sensitivity. It occurs quickly and can be life-threatening.

The symptoms of an allergic reaction can include hives and itching or symptoms throughout the entire body (anaphylaxis) including difficulty breathing, low blood pressure and can be life-threatening. A recent study shows food allergy has increased by about 50% in children over the past 20 years and continues to increase. There are now about 6 million children in the U.S. with food allergy.

What Are the Most Common Food Allergens?

Almost any food can trigger an allergic reaction, but children are most likely to be allergic to one or more of the top nine most common food allergens. 

Cow Milk 

Milk is the most common food allergy in infants and young children. Milk allergy is not the same as lactose intolerance. Lactose intolerance does not involve the immune system. 80% of individuals with a milk allergy will outgrow it by age 16.


Egg allergy is the second most common allergy in infants and young children. 70% of individuals with an egg allergy can be expected to tolerate it by age 16. The CDC, AAAAI and ACAAI all agree that it's safe for people with an egg allergy to receive the injectable flu vaccine in an appropriate setting.


More than 4 million people in the U.S. are allergic to peanuts. Because peanuts are legumes, not tree nuts, people with peanut allergies may be able to consume other types of nuts. However, 24-40% of people who are allergic to peanuts also have reactions to at least one tree nut.

Younger siblings of children allergic to peanuts may be at an increased risk for developing a peanut allergy.

Tree Nuts 

Tree nuts include, but are not limited to:

  • Almonds
  • Hazelnut
  • Cashew
  • Pistachio
  • Walnut.

If someone is allergic to one type of tree nut, they are often allergic to others. Peanuts are not a tree nut. Only 9% of children who are allergic to tree nuts will ever outgrow this allergy.


Soybeans are members of the legume family, like peanuts and other beans. Symptoms typically appear in infants and children under the age of 3, and most will outgrow the allergy by age 10.


IgE-mediated wheat allergy is most common in children and is usually outgrown during childhood. Wheat allergy is not the same as celiac disease or a gluten intolerance. About 20% of children allergic to wheat are also allergic to other grains.


A person may be allergic to all fish or specific types but this does not mean they are also allergic to shellfish. 40% of people who report a fish allergy showed no signs of the allergy until adulthood.

Crustacean Shellfish 

Shellfish includes shrimp and lobster, for example. Shellfish allergy is considered to be the most dangerous, resulting in the most emergency room visits when compared to other food allergies. Some people are sensitive to shellfish protein released into the air when it's being cooked.


Many baked goods, chips, crackers and dipping sauces contain sesame. Studies have shown that sesame allergy has significantly increased over the past 10-20 years.

Download more information on the Top 9 allergens.

When Do Food Allergies Typically Develop?

Food allergy most commonly starts in childhood. Not all food-related reactions are food allergy and, in fact, most rashes in childhood are not related to food. It often takes a detailed history and specific allergy testing to reach the diagnosis of food allergy. While some individuals may classify their food allergy as mild or severe, it is more important to know that any allergic reaction to food can cause a life-threatening condition called anaphylaxis, even if the reaction in the past was mild.

Will My Child Outgrow Their Food Allergy?

Parents often ask if it is likely that their child will outgrow a food allergy. The answer differs for various foods. Most children allergic to cow's milk, egg, soy and wheat will outgrow their allergy between 3 and 16 years of age. The prognosis for peanuts and tree nuts is much different. Clinicians previously believed that a peanut allergy is life-long, but more recent studies show that 20% of peanut-allergic children outgrow the allergy. Less than 10% of children outgrow allergy to tree nuts.

Learn More About Outgrowing a Food Allergy

Can Food Allergies Be Prevented?

Current research-based findings indicate that most children should have the highly allergenic foods introduced early in life in age-appropriate forms. Early introduction will not guarantee the child will not develop the allergy, but it is the only preventive strategy currently available. If the child’s family has a strong history of allergy, some parents feel the need to see an allergist or have an allergy test prior to introducing the food. If allergy testing is to be done, it is often best done along with a thorough allergy evaluation by a specialist. Allergy testing prior to introduction of a food runs the risk of a false positive test, meaning the test says the child has allergy but this is not the case. False positive testing can unnecessarily restrict the child’s diet and cause undue stress.

What Can Cause a Food Allergy Reaction?

Food allergy reactions happen every time the individual is exposed to the allergen. The most common exposure is eating (ingesting the food). Exposure can also happen by inhaling steam from boiling the food, or cooking the food in an open pan such as scrambling a pan of eggs or frying fish. Steaming milk for coffee can also be an issue. Touching the food will most likely only cause a reaction in the area of contact but this is not always certain. Overall, it is likely best if the allergic individual does not touch their allergen.

What are the Symptoms of an Allergic Reaction?

Allergic reactions to food can cause reactions in multiple organ systems. It is important for us to learn the signs and symptoms of an allergic reaction in order to keep children with food allergy safe. Allergic reactions usually start within minutes but can also start hours after exposure to the food. Reactions can include:

  • Hives (a raised, itchy rash)
  • Difficulty breathing
  • Difficulty swallowing
  • Hoarseness or other change in voice
  • Wheeze (musical sound with breathing)
  • Pain in the belly, with or without nausea
  • Vomiting
  • Feeling faint
  • Confusion
  • Feeling of impending doom

How Do You Treat an Allergic Reaction?

Every individual with a diagnosis of food allergy should carry an epinephrine auto-injector for emergency use, have a written plan for when to use it, and fully understand when to seek emergency care.

Learn More About Treating an Allergic Reaction

Food Allergy Program

The first of its kind in Illinois, the Food Allergy Program seeks to improve the lives of children and families affected by food allergy. Our experts provide evaluation services and comprehensive treatment, including skin prick testing, food challenges, oral immunotherapy, and education on food avoidance and managing allergic reactions.

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