What Are Food Allergies?

Food allergies occur when the immune system mistakenly identifies a harmless food protein as a threat and mounts a defense against it. This overreaction leads to a cascade of symptoms that can range from mild skin irritations to life-threatening anaphylaxis. While over 170 foods have been identified as allergens, the most common culprits include eggs, milk, peanuts, tree nuts, fish, shellfish, soy, and sesame.

Food allergies impact more than 20 million adults and children in the United States. Although there is currently no cure, proper diagnosis, avoidance strategies, and emergency preparedness can help manage the condition effectively.

Types of Food Allergies

Food allergies are broadly categorized into two main types based on immune system activity:

IgE-Mediated Food Allergies These reactions involve the immune system producing Immunoglobulin E (IgE) antibodies in response to a specific food. When the allergen is encountered again, these antibodies signal mast cells and basophils to release chemicals like histamine, leading to immediate symptoms.

Symptoms typically occur within minutes to two hours and can affect the skin, lungs, digestive tract, and cardiovascular system.

Non-IgE-Mediated Food Allergies These reactions involve other immune mechanisms, particularly in the gut. The symptoms may appear several hours or even days after exposure and primarily affect the gastrointestinal tract, though skin and respiratory symptoms may also occur.

Food Allergy vs. Food Intolerance

Food allergies involve the immune system and can lead to serious or life-threatening reactions. Food intolerances, on the other hand, are typically limited to digestive discomfort, such as bloating, gas, or diarrhea. Unlike allergies, intolerances do not involve IgE antibodies or an immune response.

Common Symptoms

Food allergy symptoms vary from person to person and may affect different organ systems:

  • Hives or itchy rash

  • Flushed or red skin

  • Swelling of the face, lips, tongue, or throat

  • Itchy or tingling mouth and nose

  • Runny nose, coughing, wheezing

  • Abdominal cramps, vomiting, diarrhea

  • Dizziness, fainting

Anaphylaxis

A severe and potentially fatal allergic reaction, anaphylaxis typically begins with mild symptoms but can escalate quickly. Signs include:

  • Difficulty breathing

  • Chest tightness

  • Swelling of the throat

  • Rapid heartbeat

  • Feeling faint or losing consciousness

Immediate administration of epinephrine is crucial. People with known food allergies should always carry an epinephrine auto-injector.

Causes and Risk Factors

Food allergies result from an abnormal immune response to specific food proteins. The body creates IgE antibodies or activates immune cells, which trigger inflammation upon subsequent exposure.

Risk factors include:

  • Family history of allergies

  • Existing allergic conditions like eczema or asthma

  • Altered gut microbiome

  • Age and sex (children and females are more commonly affected)

Diagnosis

Diagnosing food allergies involves a combination of medical history, physical examination, and diagnostic testing:

  • Skin Prick Test: Small amounts of allergens are introduced into the skin. A raised bump suggests an allergy.

  • Blood Test: Measures levels of allergen-specific IgE antibodies.

  • Elimination Diet: Suspect foods are removed from the diet and then reintroduced.

  • Oral Food Challenge: The gold standard for diagnosis, conducted under strict medical supervision.

Treatment Options

While there's no cure for food allergies, several treatment strategies can help manage the condition.

Allergen Avoidance

  • Read food labels carefully

  • Ask about ingredients when dining out

  • Be vigilant about cross-contact during food prep

Emergency Action Plan

  • Always carry an epinephrine auto-injector

  • Know how to recognize anaphylaxis

  • Share your plan with family, coworkers, and caregivers

Medications

  • Antihistamines: Help relieve mild symptoms like hives and itching

  • Corticosteroids: Used in emergencies to reduce inflammation

  • Epinephrine: First-line treatment for anaphylaxis

Oral Immunotherapy (OIT)

  • Gradual introduction of the allergen in small amounts to build tolerance

  • FDA-approved treatment available for peanut allergies (Palforzia)

Biologic Therapy

  • Xolair (omalizumab) targets IgE and helps reduce allergic response

  • Administered via injection every 2–4 weeks under medical supervision

Prevention Strategies

Preventing food allergies, especially in children, is a growing area of research:

  • Early Introduction: Introducing allergenic foods like peanuts at 4–6 months may reduce the risk

  • Breastfeeding: May offer some protective benefits

  • Gut Health: Maintaining a diverse gut microbiome may influence immune tolerance

Related Conditions

People with food allergies may also have:

  • Eczema: Up to 40% of people with eczema also have food allergies

  • Asthma: Allergies may exacerbate asthma symptoms

  • Allergic Rhinitis: Pollen allergies often co-exist with food sensitivities

  • Eosinophilic Esophagitis: An allergic condition causing inflammation in the esophagus

Living With Food Allergies

Though challenging, food allergies can be managed with proper education and preparation. Tips for living well include:

  • Communicate clearly in social and dining settings

  • Keep emergency medications on hand

  • Seek support groups or counseling if anxiety becomes overwhelming

With the right strategies, people with food allergies can lead full, active, and safe lives.