What Causes Food Allergies?

Learn about risk factors for food allergy and more.

Who develops a food allergy and why? Learn about what happens when you have a food allergy, who is most at risk and more.

What Happens During an Allergic Reaction

Your immune system’s detects and destroy germs, such as bacteria or viruses, that could make you sick, sometimes, it makes a mistake and attacks something harmless.

A food allergy happens when your immune system attacks a food protein. Your body makes its own proteins, called IgE antibodies, or immunoglobulin E, to fight against the food allergen.

When you eat or drink that food again, your body sends out the IgE antibodies to attack the allergen. This process releases chemicals that cause an allergic reaction, which can make you feel itchy, have trouble breathing, or even pass out. If you’re highly sensitive to a food, even breathing it in or having it touch your skin can trigger a reaction.

People can be allergic to any food, but eight foods cause most reactions in the U.S. These are milk, egg, peanut, tree nuts, soy, wheat, fish and shellfish.

Some people can make IgE against a certain food allergen but don’t end up developing an allergy. Some experience only mild allergies, while others are more prone to severe, life-threatening reactions. A person’s allergic reactions can vary with each exposure to the offending food, with the same amount of allergen causing mild symptoms in one instance and severe symptoms in another.


We don’t know all the causes of food allergies. But research suggests they develop from a mix of genetic and environmental influences.

Family history is known to play a role. You’re more likely to have a food allergy if a close family member does. If you have other kinds of allergic reactions – conditions like eczema, asthma or hay fever – you are also at greater risk.

You may also become more sensitive to a food allergen if you are exposed to it through air or skin contact. Having pets, livestock or siblings in your environment may lower your risk. The bacteria in your stomach (known as the microbiome) may even have something to do with it.

Risk Factors

The most important risk factors for food allergy are things you cannot change.

  • Age: Young children are more likely to develop food allergies than older children or adults (though allergies can start at any age).
  • Family history: Having a parent or sibling with a food allergy increases your risk.
  • Having another food allergy: People with food allergies tend to have more than one.
  • Having a related medical condition: Some people develop a cluster of several allergic diseases called the Atopic March. These include eczema, food allergy, allergic rhinitis and asthma.

While there is no cure for food allergies, children can outgrow them. Adults are much less likely to do so.


If you experience allergic symptoms, see your healthcare provider. Call 911 if you or someone else show signs of a severe reaction, as it could be life-threatening anaphylaxis. Let the dispatchers know that you suspect anaphylaxis, because not all ambulances are equipped to treat this medical emergency.

It is important to have your food allergy confirmed by a board-certified allergist. Food allergy symptoms overlap with symptoms of other medical conditions.


If you have a food allergy, the best way to prevent an allergic reaction is to recognize and avoid the foods that will trigger it. Always carry epinephrine with you to treat accidental exposure.

Oral immunotherapy (OIT) and the “peanut patch” are gaining traction as treatments. Their goal is to make the person less sensitive to the allergen over time. During OIT, you consume small but increasing amounts of a food allergen in a controlled setting. With the peanut patch, you wear a small adhesive containing peanut protein on the skin, replacing it daily.


Recent research tells us that early introduction of peanut (before 6 months of age), followed by regular consumption, can help protect children at high risk for peanut allergy. If you delay introduction, it can actually increase the risk. We’re still learning what this means for other food allergens.