DESCRIPTION

Food allergy is defined as an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food. Most commonly, the protein component of the food is responsible for the adverse immunologic response.

• Classifications of food allergies:
  • Immunoglobulin E (IgE)-mediated
    • Classical food allergy/IgE-mediated food allergy
    • Pollen food allergy syndrome/oral allergy syndrome (cross-reactivity between food protein and pollens)
    • Galactose-α-1,3-galactose allergy (allergy to carbohydrate moiety)
  • Non–IgE-mediated (cell-mediated)
    • Food protein–induced enterocolitis syndrome (FPIES)
    • Food protein–induced allergic proctocolitis (FPIAP); often referred to as “milk protein allergy”
    • Celiac disease
  • Mixed IgE and non–IgE-mediated
    • Atopic dermatitis
    • Eosinophilic gastroenteropathies (eosinophilic esophagitis [EoE], eosinophilic gastroenteritis)
• Most common IgE-mediated food allergies in children:
  • Cow’s milk
  • Egg
  • Wheat
  • Peanut
  • Tree nut
  • Soy
• Most common causes of FPIES:
  • Cow’s milk
  • Soy
  • Grains (rice, oat)
• Most common causes of FPIAP:
  • Cow’s milk
  • Egg
  • Soy

EPIDEMIOLOGY

• Food-induced anaphylaxis is one of the most common causes of pediatric and adolescent anaphylactic reactions in the United States. The prevalence of food allergy has increased over the past 10 to 20 years.
• 8% of children and 10% of adults have food allergy.
• Prevalence and natural history of IgE-mediated food allergies in children and adults:
  • Milk: 0.5–5%; 50% outgrow by late childhood.
  • Egg: 1.2–10%; 50% outgrow by late childhood.
  • Peanut: 0.2–4.5%; only 22% outgrow by 4 years of age.
  • Tree nuts: 2%; only 10% outgrow by late childhood.
  • Shellfish: up to 10%, typically persistent allergy
  • Fish: up to 7%, typically persistent allergy

GENERAL PREVENTION

For IgE-mediated food allergy:

• Delaying introduction of highly allergenic food in high-risk infants increases risk of developing an IgE-mediated food allergy.
• Current recommendations are to begin adding allergenic solid foods between 4 and 6 months of age in all infants without screening, regardless of baseline risk, prioritizing peanut and egg.

RISK FACTORS

For IgE-mediated food allergy:

• Atopic dermatitis
• Presence of other food allergies
• Family history of atopy
• Delayed introduction of allergenic foods into diet
• Genetic

PATHOPHYSIOLOGY

• Oral tolerance to food proteins is believed to develop through T-cell anergy or induction of regulatory T cells.
• Food hypersensitivity develops when oral tolerance fails to develop or breaks down.
• IgE-mediated: T cells induce B cells to produce IgE antibodies that initially bind on the surface of mast cells and basophils; when reexposed, the food protein antigen binds to these IgE antibodies, leading to degranulation of the cells and release of histamine and other chemical mediators
• Non–IgE-mediated (cell-mediated): less clearly characterized; food proteins cause local inflammation mediated by T cells, leading to inflammatory cell infiltrates and increased vascular permeability. Subacute and chronic inflammation of this type primarily affects the GI tract.
• Mixed IgE and non–IgE-mediated: Eosinophil-associated GI disorders (EGIDs) are characterized by inappropriate eosinophilic infiltration in the GI tract tissue, such as the esophagus, stomach, or bowel.

COMMONLY ASSOCIATED CONDITIONS

• Atopic dermatitis
• Asthma
• Allergic rhinitis
• EoE
• Other atopic diseases