Food allergy is just one way your child can react to a food. When your child has an allergic reaction to a food, the immune system mistakenly sees and responds to a normal protein found in a food as an invader. There are a number of immune reactions to foods.
The most common immune reaction involves the creation of an immunoglobulin E (IgE) antibody. IgE is linked to allergies. This antibody attacks the protein and triggers an allergic reaction.
IgE causes an exaggerated or hyper-response to something that would not ordinarily cause a problem. The IgE that your child’s body produces attaches to specific cells in the body. These are special cells called mast cells. Mast cells are found in the skin, the digestive tract, the respiratory system and the circulatory system. When the IgE antibody on the mast cell meets the specific food protein, a reaction occurs.
Most food allergies are linked to eight specific foods. Those foods are:
- Cow’s milk
- Tree nuts
Food allergies are most common in babies and children, but they can appear at any age. Children may outgrow a food allergy, particularly one to milk or eggs. In the past, it was thought that peanut and tree nut allergies would last forever. Now, 20 percent of children with peanut allergy and 10 percent of children with tree nut allergy may outgrow these allergies, too.
Having a food allergy may also mean that your child may have other allergies. For example, a child who is allergic to bananas or melons may also be allergic to ragweed because the proteins that trigger the allergy are similar. This is called cross-reactivity.
Another example of cross-reactivity is the occurrence of positive allergy tests to legumes in a child with a peanut allergy. Cross-reactive test results often do not mean there is clinical reactivity. This is a good example of a falsely positive allergy test result.
Cross-reactivity happens when different allergens contain shared proteins or proteins that your child’s immune system sees as being very similar. Directed allergy testing and an oral food challenge may determine if a reaction to a food is due to cross-reactivity.
Common symptoms of a food allergy include:
- Anaphylaxis (a severe, sudden and potentially life-threatening allergic reaction)
- Acute hives and swelling (short, one-day episode of hives and angioedema)
- Atopic dermatitis flare-up
- Gastrointestinal reactions like vomiting and diarrhea
Food allergy symptoms occur right away. The amount of the trigger food does not matter. Even a small exposure can cause an allergic reaction. These symptoms will occur every time your child eats the allergenic food.
In some cases, you may think your child has a food allergy when he or she actually has a food intolerance. With food intolerance, the reactions that occur do not involve the immune system. Small amounts of the food are usually fine, but larger quantities may cause digestive problems like gas, cramps or bloating. IgE testing does not help with this type of nonallergic food reaction.
Diagnosis of Food Allergy
Diagnosing a food allergy starts with a doctor’s appointment with a Riley at IU Health allergy specialist. During this appointment, the doctor will learn about your child's health history and perform a physical exam. Make sure to tell the doctor about any cause and effect relationships you have noticed with your child’s symptoms and certain foods.
Allergy testing is done to confirm a suspected food allergy diagnosis. The skin test is the standard. A blood test may be done for a positive food skin test to help establish the risk of a reaction. A food challenge can also help confirm a diagnosis. Once a suspected food is confirmed as an allergen, a treatment plan is created.
- Epinephrine. If your child’s food allergy causes a severe reaction like anaphylaxis or if he or she has a peanut, tree nut, fish or shellfish allergy, his or her doctor will prescribe injectable epinephrine regardless of the symptoms. You will receive instructions for when, how and why to use injectable epinephrine as well as what to do after its use. Injectable epinephrine prescriptions always come with a trainer device so other family members and caregivers who are in contact with your child can become comfortable with their correct use.
- Medical alert bracelet. This can help protect your child. A medical alert bracelet warns other parents and adults that certain types of foods can be life-threatening to your child. It can also tell an adult what is happening if there is a reaction.
- Food action plan. This is a plan that spells out what to avoid and how to handle a reaction.
- Re-evaluation. After a year or more of avoiding foods, your child may need to have more allergy testing to see whether there is any change in the food allergy. This would include skin and blood testing. The blood test results can help determine if the food allergy is going away and what the risk of a reaction would be if your child were exposed to the food.
Based on your child’s allergy symptoms and allergy test results, his or her allergist may also recommend a food challenge.
There is hope on the horizon for treating food allergies and preventing the development of food allergy. Allergists at Riley at IU Health can help guide food allergy prevention strategies. Food allergy treatments are in development, and we will see these in the near future.
Key Points to Remember
Key Points to Remember
- Food allergy occurs when your child’s immune system mistakenly sees a normal protein found in certain foods as an invader and makes antibodies to attack it.
- Most food allergies involve one of eight foods: cow’s milk, eggs, fish, shellfish, peanuts, tree nuts, wheat or soy.
- At this time, the only effective treatment for food allergy is for your child to avoid the food that triggers an allergic reaction.
- If your child’s food allergy causes a severe reaction like anaphylaxis or if he or she has a peanut, tree nut, fish or shellfish allergy, his or her doctor will prescribe injectable epinephrine regardless of the symptoms.
Support Services & Resources
Support Services & Resources
Visit the trusted websites below to learn more about food allergies.
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
This website provides in-depth information for families of children with food allergies.
The American Academy of Allergy, Asthma & Immunology provides additional information about food allergies, including diagnosis and treatment.
The American College of Allergy, Asthma & Immunology provides additional information about food allergies, including diagnosis and treatment.
This resource from the National Institutes of Health provides clinical recommendations for healthcare professionals on how to diagnose and manage food allergy and how to treat acute food allergy reactions.