Food Allergy

Food allergy is a part of a larger group of designated adverse reactions to food. Food allergy is caused by a specific immune response which occurs due to exposure to a specific food. When exposed, the immune system overreacts by producing antibodies called Immunoglobulin E (IgE) which ultimately cause an allergic reaction.

What Are the Most Common Food Allergens?

Foods that cause allergy are called allergens. The most common food allergens are:

  • Cow milk
  • Egg
  • Peanut
  • Tree nuts (cashew and walnut, for example)
  • Soy
  • Wheat
  • Fish
  • Crustacean shellfish (shrimp and lobster, for example)
  • Sesame 

When Do Food Allergies Typically Develop?

Food allergy most commonly starts in childhood. Not all food-related reactions are food allergy and 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 it may seem common for individuals to classify their food allergy as severe (or not), food allergy to any food can cause a life-threatening condition called anaphylaxis. The need to identify the risk of this severe reaction is the reason to determine if a child has food allergy or if there is another reason for the adverse reaction to food. 

Can Food Allergies Be Prevented?

While allergic disorders do run in families, why an individual develops food allergy versus another type of allergy is unknown. Current research-based findings indicate that a child 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 allergy test prior to introduction but this is not generally recommended. If allergy testing is to be done, it is often best that it is done based on 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 Side Effects of a Food Allergy Reaction?

Allergic reactions to food can cause reactions in multiple organ systems. The reactions happen generally within two hours of the exposure to the food but can often happen within minutes. 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

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.

Other Helpful Resources

Visit the following websites for more information on food allergies.

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