Food Allergy

Overview

Food allergies occur when the immune system overreacts to proteins found in certain foods, treating them as harmful invaders. This immune response can affect multiple organ systems, including the skin, gastrointestinal tract, respiratory system, and cardiovascular system. Unlike food intolerances, which typically cause digestive discomfort, food allergies involve the immune system and can be potentially life-threatening.

The most common food allergens, often referred to as the "Big 9," account for approximately 90% of all food allergic reactions. These include milk, eggs, peanuts, tree nuts, wheat, soy, fish, shellfish, and sesame. While some children outgrow certain food allergies, particularly those to milk, egg, and soy, allergies to peanuts, tree nuts, fish, and shellfish tend to persist into adulthood.

Food allergies can significantly impact quality of life, requiring constant vigilance in food selection, careful label reading, and preparedness for potential allergic reactions. The psychological burden on individuals and families dealing with food allergies is substantial, affecting social activities, travel, and daily meal planning. Understanding and properly managing food allergies is crucial for preventing severe reactions and maintaining a healthy, active lifestyle.

Symptoms of Food Allergy

Food allergy symptoms can appear within minutes to two hours after consuming the trigger food, though most reactions occur within 30 minutes. The severity of reactions can vary significantly between individuals and even between different exposures in the same person. Recognizing these symptoms quickly is crucial for appropriate treatment.

Common Symptoms

• Lip swelling - Often one of the first signs, lips may tingle before swelling
• Skin rash - Hives, eczema flare-ups, or general redness and itching
• Itching of skin - Can occur anywhere on the body, often accompanying hives
• Abnormal appearing skin - Includes hives, welts, or patches of inflamed skin
• Vomiting - Often occurs shortly after eating the trigger food
• Allergic reaction - Systemic response involving multiple body systems
• Hand or finger swelling - Angioedema affecting the extremities
• Nasal congestion - Stuffy or runny nose, similar to hay fever symptoms
• Cough - Persistent coughing, may indicate respiratory involvement

Severe Symptoms (Anaphylaxis)

Anaphylaxis is a severe, potentially life-threatening allergic reaction requiring immediate medical attention:

• Difficulty breathing - Wheezing, shortness of breath, or throat tightness
• Rapid pulse - Heart racing or palpitations
• Dizziness - Feeling faint or loss of consciousness
• Severe drop in blood pressure - Can lead to shock
• Throat swelling - Feeling of throat closing or difficulty swallowing
• Abdominal pain - Severe cramping or pain

Gastrointestinal Symptoms

• Diarrhea - May occur immediately or hours after exposure
• Nausea - Often precedes vomiting
• Stomach cramps - Can range from mild to severe

It's important to note that symptoms can progress rapidly from mild to severe. Any sign of breathing difficulty, throat swelling, or multiple body systems being affected should be treated as a medical emergency requiring immediate administration of epinephrine and calling emergency services.

Causes of Food Allergy

Food allergies develop when the immune system mistakenly identifies specific food proteins as dangerous substances. This misidentification triggers a complex cascade of immune responses designed to protect the body from what it perceives as a threat.

The Immune Response Process

Initial Sensitization: Upon first exposure to an allergen, the immune system produces Immunoglobulin E (IgE) antibodies specific to that food protein. These antibodies attach to mast cells and basophils throughout the body, particularly in areas like the skin, respiratory tract, and gastrointestinal system.

Subsequent Exposure: When the person consumes the food again, the allergen binds to the IgE antibodies on the mast cells, triggering these cells to release inflammatory chemicals including histamine, leukotrienes, and cytokines. This release causes the various symptoms associated with allergic reactions.

Common Food Allergens

The "Big 9" allergens responsible for most food allergies:

• Milk: The most common childhood allergy, affecting 2-3% of young children
• Eggs: Often outgrown by adolescence, but can persist into adulthood
• Peanuts: A leading cause of severe allergic reactions
• Tree nuts: Including almonds, cashews, walnuts, pecans, and others
• Wheat: Different from celiac disease, which is an autoimmune condition
• Soy: More common in infants and young children
• Fish: Usually lifelong once developed
• Shellfish: The most common adult-onset food allergy
• Sesame: Recently recognized as a major allergen in many countries

Cross-Reactivity

Cross-reactivity occurs when proteins in one food are similar to proteins in another, causing allergic reactions to multiple foods:

• Oral Allergy Syndrome: People with pollen allergies may react to raw fruits and vegetables
• Shellfish and Dust Mites: Share similar proteins, potentially causing cross-reactions
• Latex-Fruit Syndrome: Latex allergy associated with reactions to bananas, avocados, and kiwi

Risk Factors

Several factors can increase the likelihood of developing food allergies or experiencing severe reactions:

Primary Risk Factors

• Family history: Having parents or siblings with any type of allergy increases risk by 40-70%
• Age: Food allergies are most common in children, affecting up to 8% of those under age 5
• Other allergic conditions: Presence of asthma, eczema, or allergic rhinitis
• Previous allergic reactions: History of reactions increases risk of future, potentially more severe reactions

Environmental and Lifestyle Factors

• Early exposure timing: Introduction of allergenic foods too early or too late in infancy
• Hygiene hypothesis: Limited early exposure to bacteria and infections may increase allergy risk
• Vitamin D deficiency: Low levels associated with increased food allergy risk
• Cesarean delivery: May affect gut microbiome development and allergy risk
• Formula feeding: Early introduction of cow's milk formula may increase milk allergy risk

Factors Affecting Reaction Severity

• Amount consumed: Larger quantities typically cause more severe reactions
• Food preparation: Raw foods may cause stronger reactions than cooked
• Exercise: Physical activity after eating can worsen reactions
• Alcohol consumption: Can increase absorption and reaction severity
• Concurrent illness: Infections or stress can lower reaction threshold
• Medications: Beta-blockers and ACE inhibitors can worsen reactions

Diagnosis

Accurate diagnosis of food allergies is crucial for proper management and avoiding unnecessary dietary restrictions. The diagnostic process typically involves a combination of medical history, physical examination, and specific allergy tests.

Medical History and Physical Examination

The allergist will gather detailed information about:

• Suspected trigger foods and timing of reactions
• Specific symptoms experienced and their severity
• Family history of allergies or allergic conditions
• Current medications and medical conditions
• Dietary habits and previous elimination attempts

Diagnostic Tests

Skin Prick Test (SPT): Small amounts of food extracts are placed on the skin, which is then pricked to allow exposure. A raised bump (wheal) indicates possible allergy. Results appear within 15-20 minutes. False positives are common, so results must be interpreted alongside clinical history.

Blood Tests (Specific IgE): Measures the amount of allergen-specific IgE antibodies in the blood. Commonly uses ImmunoCAP technology. Less sensitive than skin tests but useful when skin testing isn't possible due to severe eczema or medications.

Oral Food Challenge (OFC): The gold standard for food allergy diagnosis. Patient consumes gradually increasing amounts of the suspected food under medical supervision. Must be performed in a facility equipped to handle severe reactions. Double-blind, placebo-controlled challenges are most accurate.

Component Testing: Advanced blood testing that identifies specific protein components within foods. Helps predict reaction severity and likelihood of outgrowing allergies. Particularly useful for peanut, milk, and egg allergies.

Elimination Diet

Suspected foods are removed from the diet for 2-4 weeks, then reintroduced one at a time while monitoring for reactions. Useful for identifying delayed reactions or non-IgE mediated allergies. Should be supervised by a healthcare professional to ensure nutritional adequacy.

Tests to Avoid

Several unproven tests are not recommended for diagnosing food allergies:

• IgG testing for food allergies
• Hair analysis
• Applied kinesiology
• Electrodermal testing
• Pulse testing

Treatment Options

Management of food allergies focuses primarily on strict avoidance of trigger foods and preparedness for accidental exposures. Recent advances have introduced new treatment options that may help some individuals build tolerance to their allergens.

Avoidance and Management

Strict Allergen Avoidance: The cornerstone of food allergy management:

• Reading all food labels carefully, including checking for "may contain" warnings
• Understanding ingredient lists and recognizing alternate names for allergens
• Communicating clearly with restaurants about allergies and cross-contamination risks
• Avoiding cross-contact during food preparation at home
• Creating allergen-free zones in shared kitchens

Emergency Medications

Epinephrine Auto-injectors: First-line treatment for anaphylaxis:

• Should be carried at all times by those at risk for severe reactions
• Available in different doses for children and adults
• Typically prescribed in sets of two in case a second dose is needed
• Requires training on proper use and regular checks of expiration dates
• Common brands include EpiPen, Auvi-Q, and generic versions

Antihistamines: For mild allergic reactions:

• Can help with itching, hives, and mild swelling
• Should never replace epinephrine for severe reactions
• Available in oral and liquid forms
• May mask early signs of anaphylaxis

Immunotherapy Approaches

Oral Immunotherapy (OIT): FDA-approved for peanut allergy (Palforzia):

• Involves consuming gradually increasing amounts of allergen
• Aims to increase threshold for reactions, not cure allergy
• Requires ongoing daily dosing to maintain protection
• Risk of reactions during treatment
• Being studied for other food allergens

Sublingual Immunotherapy (SLIT): Allergen extracts placed under the tongue:

• Generally safer than OIT with fewer side effects
• May be less effective than OIT
• Still experimental for most food allergies

Epicutaneous Immunotherapy (EPIT): Allergen delivered through skin patches:

• Currently in clinical trials for peanut and milk allergies
• May have fewer systemic reactions than OIT
• Viaskin Peanut patch awaiting FDA approval

Emerging Treatments

• Anti-IgE therapy (Omalizumab): May reduce reaction severity when combined with OIT
• Chinese herbal formulas: FAHF-2 showing promise in clinical trials
• Probiotics and prebiotics: Being studied for prevention and treatment
• Modified allergen proteins: Engineered to reduce allergenicity while maintaining effectiveness

Supportive Care

• Nutritional counseling: Ensuring adequate nutrition while avoiding allergens
• Psychological support: Managing anxiety and quality of life impacts
• Medical alert identification: Bracelets or cards listing allergies
• Action plans: Written emergency plans for home, school, and work

Prevention

While not all food allergies can be prevented, recent research has identified strategies that may reduce the risk of developing allergies, particularly in high-risk infants. Prevention focuses on early introduction of allergenic foods and maintaining exposure.

Early Introduction Guidelines

Current recommendations based on landmark studies like LEAP (Learning Early About Peanut):

• High-risk infants: Introduce peanut products between 4-6 months after evaluation
• Moderate-risk infants: Introduce around 6 months at home
• Low-risk infants: Introduce with other solid foods as desired
• Other allergens: Introduce eggs, milk, and other common allergens early and regularly
• Maintain exposure: Continue regular consumption after introduction

Maternal Factors

• During pregnancy: No need to avoid allergenic foods unless mother is allergic
• Breastfeeding: May provide some protection; continue eating diverse diet
• Vitamin D: Adequate levels during pregnancy may reduce allergy risk
• Probiotics: Some evidence for beneficial effects during pregnancy and infancy

Environmental Modifications

• Diverse diet: Expose children to variety of foods early
• Avoid unnecessary delays: Don't postpone allergen introduction without medical reason
• Skin barrier: Treat eczema aggressively to prevent sensitization through skin
• Hygiene balance: Allow appropriate microbial exposure while maintaining cleanliness

For Those with Existing Allergies

• Prevent reactions: Careful label reading and communication
• Cross-contamination: Use separate utensils and preparation areas
• Education: Train family, caregivers, and school personnel
• Emergency preparedness: Always carry epinephrine and have action plan

When to See a Doctor

Knowing when to seek medical attention for food allergies is crucial for proper diagnosis, management, and emergency treatment. Different situations require different levels of medical urgency.

Seek Emergency Care (Call 911) For:

• Any signs of anaphylaxis, including difficulty breathing or swallowing
• Swelling of face, lips, tongue, or throat
• Rapid pulse, dizziness, or feeling faint
• Severe whole-body reaction (hives with other symptoms)
• Confusion or loss of consciousness
• Severe abdominal pain with other allergic symptoms
• Feeling of impending doom

Schedule an Appointment for:

• Suspected food allergy based on consistent reactions
• Family history of allergies and introducing solid foods to infant
• Unexplained chronic symptoms possibly related to foods
• Need for allergy testing or food challenge
• Management plan for diagnosed food allergies
• Interest in immunotherapy options
• Nutritional concerns due to food restrictions

See an Allergist When:

• Multiple food allergies are suspected
• Previous severe reactions have occurred
• Diagnosis is unclear after initial evaluation
• Considering oral immunotherapy
• Child has eczema and you're planning food introduction
• Need for oral food challenge testing

Remember: If epinephrine is administered for an allergic reaction, always call 911 or go to the emergency room immediately, even if symptoms improve. Biphasic reactions can occur hours later.

Related Conditions

Food allergies often coexist with other allergic and immune-mediated conditions. Understanding these relationships helps in comprehensive management.

Allergic Conditions

• Atopic Dermatitis (Eczema) - Often precedes food allergy development
• Asthma - Increases risk of severe food allergy reactions
• Allergic Rhinitis - Part of the "atopic march"
• Eosinophilic Esophagitis - Can be triggered by food allergens

Other Food-Related Conditions

• Celiac Disease - Autoimmune reaction to gluten, not an allergy
• Lactose Intolerance - Enzyme deficiency, not immune-mediated
• Oral Allergy Syndrome - Cross-reaction with pollen allergies
• FPIES - Food protein-induced enterocolitis syndrome

Related Symptoms

• Anaphylaxis - Severe allergic reaction
• Angioedema - Deep tissue swelling
• Urticaria (Hives) - Common allergic skin reaction

Frequently Asked Questions