Food Allergy

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Food allergies are adverse health effects arising from a specific immune response that occurs reproducibly on exposure to a given food. Immune responses can be IgE-mediated or non-IgE-mediated. This chapter focuses on IgE-mediated food allergy.

Description

  • A reproducible hypersensitivity reaction related to specific food exposures mediated by IgE
  • System(s) affected: gastrointestinal (GI), heme/lymphatic/immunologic, pulmonary, skin, cardiovascular
  • Synonym(s): IgE-mediated food reactions, food hypersensitivity, anaphylaxis, allergic reaction

Epidemiology

  • Found at all ages
  • Traditionally felt more common in infants and young children
  • Increasing prevalence in adults (1)
  • Predominant sex: male > female in children, female > male in adults
  • May disproportionately impact in underserved and minority populations

Incidence

Egg allergy incidence has been reported as 1.23% in infants, whereas this number for cow’s milk allergy was 0.54%.

Prevalence

  • 3% prevalence of IgE-mediated food allergy as assessed by an oral food challenge (OFC) the diagnostic gold standard.
  • Self-reported prevalence of food allergy is >10%: with 1 in 10 adults and 1 in 12 children.
  • In children, the most common food allergies are cow’s milk (2%), egg (0.6–0.8%), peanut (1.2–2%), and tree nuts (approximately 1%) (2).
  • Adults more commonly have allergies to shellfish (2.9%), milk (1.9%), peanuts (1.8%), tree nuts (1.2%), and fish (0.9%) (3).
  • Most children outgrow milk and egg allergy; 30% of children with peanut allergy outgrow by school age.

Etiology and Pathophysiology

  • Allergic reactions to food are a result of incomplete of immunologic tolerance to protein-based allergens in food, resulting in immune-mediated systemic responses.
  • Any ingested substance can cause allergic reactions:
    • 90% of food allergies in the United States involve cow’s milk, egg white, wheat, soy, peanut, tree nuts (e.g., walnut, pecan, cashew, and pistachio), fish, shellfish, and sesame.
    • Food dyes and additives are rare causes of allergy.

Genetics

  • HLA alleles have been identified as genetic determinants for peanut allergy.
  • Food allergy screening is currently not recommended for siblings of food allergy patients.

Risk Factors

  • Sex (male children, female adults)
  • Race/ethnicity (Asian and Black children at higher risk)
  • Allergic or atopic predisposition (particularly eczema)
  • Family history of food hypersensitivity

General Prevention

  • High-risk infants who are regularly fed peanut protein (6 g/week) have 80% risk reduction in developing peanut allergy by age 5 years
  • Current recommendations for food allergy prevention through nutrition include:
    • Introduce peanut and egg to all infants around 6 months of age, but not before 4 months.
    • Do not deliberately delay the introduction of other allergenic foods.
  • Have epinephrine autoinjectors for patients at risk for anaphylaxis.

Commonly Associated Conditions

  • Food protein-induced enterocolitis syndrome (FPIES); eosinophilic esophagitis
  • Atopic dermatitis; asthma; allergic rhinitis

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