NIAID-Sponsored Food Allergy Guidelines (J Allergy Clin Immunol 2010;126:S1)
www.niaid.nih.gov/topics/foodAllergy/clinical/Documents/FAGuidelinesExecSummary.pdf
Definition (Pediatrics 2011;128:955)
• Food allergy (FA): Adverse health effect arising from a specific response that occurs reproducibly on exposure to a given food
• Anaphylaxis: A serious immunologic reaction that is rapid in onset and may cause death (see ED chapter for more on anaphylaxis)
Classification (Pediatr Clin N Am 2011;58:315)
• IgE mediated: Urticaria/angioedema, rhinoconjunctivitis/asthma, anaphylaxis, pollen-food allergy syndrome (PFAS) (aka oral allergy syndrome (OAS))
• Mixed IgE and cell mediated: Atopic dermatitis (AD), eosinophilic gastrointestinal disorders (EGIDs)
• Cell mediated: Dietary protein-induced proctitis/proctocolitis, food protein-induced enterocolitis syndrome (FPIES), Celiac disease, Heiner syndrome
Pathophysiology (Annu Rev Med 2009;60:261)
• IgE mediated: Dendritic cells interact with dietary antigens → T-helper-2 response → B-cell IgE production → IgE binds on the surface of mast cells
• PFAS: Cross-reactivity btw proteins in pollen & proteins in certain fruits/veg
• FPIES: May relate to increased TNF-α, decreased TGF-β
Epidemiology (Pediatr Clin N Am 2011;58:327)
• Self-reported FA is 10 times higher than what can be confirmed with testing
• FA is more common in early childhood and decreases with age
• Self-reported FA ranges from 3–35%; confirmed FA ranges from 1–10.8%
• Most common allergens (kids): Cow’s milk, egg, wheat, soy, peanut/tree nut, fish/shellfish
Clinical Manifestations (Pediatr Clin N Am 2011;58:315)
• IgE-mediated: Onset of sx min to 2 hr after ingestion (urticaria, angioedema, rhinoconjunctivitis, asthma, GI sx, anaphylaxis) vs. Cell Mediated: Delayed rxn
• OAS: Pruritis, tingling, mild swelling of lips, tongue, palate, and throat; 10% have systemic findings; 1–2% develop anaphylaxis
• Eosinophilic esophagitis: Presentation varies w/ age: Feeding difficulty + FTT in young kids, vomiting + abd pain in older kids, dysphagia + food impaction in teens
• Eosinophilic gastroenteritis: Abd pain, nausea, diarrhea, weight loss 2/2 malabsorption
• Dietary protein-induced proctitis/proctocolitis: Typically breastfed infants age 2–8 wk, mucus + blood in stools but otherwise well-appearing, removing allergenic food from mother’s diet leads to rapid improvement
• FPIES: Peak incidence 1 wk–3 mo, usually formula fed; severe GI symptoms: Vomiting, diarrhea, FTT, anemia, hypotension and lethargy 2/2 dehydration
Evaluation (J Allergy Clin Immunol 2010;126:S1, Ann Allergy Asthma
Immunol 2006;96:S1, J Allergy Clin Immunol 2004;114:213)
• History is key: Identify culprit foods, time course of rxn, quantity ingested, ancillary factors, Hx of similar sx, and FHx and personal hx of atopy
• IgE mediated: Skin prick testing (SPT) and specific serum IgE (sIgE) measurements can be helpful but not diagnostic; to avoid false+, pts should be tested only to suspect foods and when there is high pretest probability
• Skin prick tests (for IgE-mediated disorders): A wheal ≥3 mm is considered positive
• SPT: Sensitivity >90%; specificity approx 50%
• CAP-FEIA (formerly RAST): Measures food-specific serum IgE
• ImmunoCAP is the preferred CAP-FEIA
• Double-blind, placebo-controlled food challenge gold std for dx; only in controlled setting; should be done if dx of FA unclear or to confirm suspected resolution of FA
• EGIDs: SPT, sIgE, atopy patch testing may be helpful but mucosal bx needed for dx
• Dietary protein-induced proctitis/proctocolitis/FPIES: Dx based on history, sx resolution with causative food elimination, and sx recurrence with food challenge
Management and Prevention (Pediatrics 2011;128:955, Pediatr Clin N Am 2011;58:481, J Allergy Clin Immunol 2011;127:654)
• Key to mgmt is avoidance of allergen (www.foodallergy.org has practical tips)
• Tx: Antihistamines for OAS and nonsevere rxns, epi for all pts w/ systemic rxns
• Current research for tx of FA includes immunotherapy and anti-IgE antibodies
• Oral immunotherapy has been shown to induce desensitization and enable patients to ingest a greater amount of allergenic food protein
• Restricting mother’s diet in pregnancy or lactation to prevent FA not recommended
• No evidence that delayed intro of solid food >4 mo prevents FA and some evidence that delayed intro of solids may promote allergy
• Vaccines containing egg include influenza, MMR, yellow fever, rabies
• MMR vaccine is not contraindicated for children with egg allergy
• Flu vaccine: If mild rxn to egg (hives only) → safe to give vaccine in office with precautions (resuscitative equipment available and observe pt for 30 min); if
severe rxn (CV, resp, GI sx) → allergy consultation for evaluation of egg allergy and vaccine administration (Pediatrics 2011;128:813–825)