Residency · Residency · Medicine Pediatrics
Food Allergy: Prevention, Diagnosis, and Management
Introduction
Food allergy affects approximately 8% of children and 10% of adults in the United States, with prevalence rising over the past two decades. IgE-mediated food allergy represents the most clinically significant form, capable of causing life-threatening anaphylaxis. Med-peds physicians must understand evolving paradigms in early allergen introduction, accurate diagnostic strategies, and emergency management across the age spectrum.
Epidemiology and Risk Factors
The "big nine" allergens account for >90% of reactions: milk, egg, peanut, tree nuts, wheat, soy, fish, shellfish, sesame. Childhood prevalence peaks in the first two years of life; milk and egg allergies often resolve by school age. Peanut, tree nut, and shellfish allergies tend to persist into adulthood. Risk factors include atopic dermatitis, family history of atopy, and filaggrin gene mutations. The dual allergen exposure hypothesis proposes that cutaneous sensitization through disrupted skin promotes allergy, while early oral exposure promotes tolerance.
Prevention Strategies
Early Allergen Introduction
The LEAP trial demonstrated that early peanut introduction (4-11 months) reduced peanut allergy by 81% in high-risk infants. Current guidelines recommend introducing peanut-containing foods around 4-6 months in infants with severe eczema or egg allergy after evaluation. The EAT study supported early introduction of multiple allergens, though adherence was challenging. Breastfeeding is encouraged but is not independently protective against food allergy.
Role of the Skin Barrier
Aggressive treatment of atopic dermatitis with emollients and topical anti-inflammatories may reduce transcutaneous sensitization. Avoidance diets during pregnancy and lactation are no longer recommended for allergy prevention.
Diagnosis
Clinical History
Detailed history should characterize the timing (minutes to hours), reproducibility, and specific symptoms of reactions. Distinguish IgE-mediated (urticaria, angioedema, anaphylaxis) from non-IgE-mediated (FPIES, eosinophilic esophagitis) and mixed presentations. In adults, consider cofactors such as exercise, alcohol, and NSAIDs that lower the reaction threshold.
Diagnostic Testing
| Test | Sensitivity | Specificity | Best Use | Limitations |
|---|---|---|---|---|
| Skin prick test (SPT) | ~90% | ~50% | Initial screening; rapid results | Cannot use with antihistamines; risk of reaction |
| Serum-specific IgE | ~90% | ~50% | When SPT not feasible; trending over time | Does not confirm clinical reactivity |
| Component-resolved diagnostics | Variable | Higher than whole-allergen | Distinguishing true allergy from cross-reactivity | Limited allergens available |
| Oral food challenge (OFC) | Gold standard | Gold standard | Definitive diagnosis; assessing resolution | Requires medical supervision; time-intensive |
Skin prick testing (SPT): High sensitivity (~90%), moderate specificity; a wheal >=3 mm above negative control is positive. Serum-specific IgE: Useful when SPT is not feasible; values above predictive decision points increase likelihood of clinical reactivity. Component-resolved diagnostics (CRD): Identifies specific allergenic proteins (e.g., Ara h 2 for peanut) to improve specificity. Oral food challenge (OFC): The gold standard for diagnosis; performed under medical supervision.
Management
Allergen Avoidance
Strict dietary avoidance remains the cornerstone of management. Educate families on label reading, cross-contact risks, and restaurant safety. In pediatric patients, ensure nutritional adequacy with dietitian involvement when eliminating major food groups.
Emergency Preparedness
All patients with IgE-mediated food allergy should carry epinephrine auto-injectors and have an anaphylaxis action plan. Epinephrine dosing: 0.01 mg/kg IM (max 0.3 mg in children <30 kg, 0.5 mg in adults) Train patients, caregivers, and school personnel on device use. Antihistamines treat cutaneous symptoms but do not substitute for epinephrine in anaphylaxis.
Immunotherapy and Emerging Treatments
Palforzia (peanut oral immunotherapy) is FDA-approved for ages 4-17 to reduce severity of accidental exposures. Omalizumab (anti-IgE) is approved as adjunct therapy for food allergy, reducing reaction severity. Epicutaneous immunotherapy (EPIT) and sublingual immunotherapy (SLIT) are under investigation. Desensitization does not equate to sustained unresponsiveness; ongoing dosing is typically required.
Special Populations
FPIES: Non-IgE-mediated; presents with profuse vomiting 1-4 hours after ingestion; managed with avoidance and ondansetron for acute episodes. Eosinophilic esophagitis: Overlaps with food allergy; requires endoscopic evaluation and elimination diets or swallowed topical corticosteroids. Adult-onset food allergy: Increasingly recognized; shellfish and tree nuts are common culprits.
Clinical Pearls
Early introduction of allergenic foods in high-risk infants is now standard of care and has shifted prevention paradigms. A positive skin prick test or specific IgE alone does not confirm clinical allergy; oral food challenge remains the gold standard. Epinephrine is the first-line treatment for anaphylaxis; delays in administration are associated with fatal outcomes. Oral immunotherapy reduces reaction severity but does not cure food allergy; shared decision-making is essential. Non-IgE-mediated food allergies (FPIES, EoE) require different diagnostic and management frameworks.
References
- Du Toit G, Roberts G, Sayre PH, et al. Randomized trial of peanut consumption in infants at risk for peanut allergy (LEAP). N Engl J Med. 2015;372(9):803-813.
- Togias A, Cooper SF, Acebal ML, et al. Addendum guidelines for the prevention of peanut allergy in the United States. J Allergy Clin Immunol. 2017;139(1):29-44.
- Sampson HA, Aceves S, Bock SA, et al. Food allergy: A practice parameter update. J Allergy Clin Immunol. 2014;134(5):1016-1025.
- PALISADE Group. AR101 oral immunotherapy for peanut allergy. N Engl J Med. 2018;379(21):1991-2001.