Food Allergy

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Basics

Food allergy is defined as an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.

Description

  • Hypersensitivity reaction related to certain food exposures; can involve IgE-mediated and non–IgE-mediated mechanisms
  • System(s) affected: gastrointestinal (GI), heme/lymphatic/immunologic, pulmonary, skin/exocrine
  • Synonym(s): allergic bowel disease; dietary protein sensitivity syndrome

Epidemiology

  • Predominant age: all ages but more common in infants and children
  • Predominant sex: male > female (2:1)
  • Disproportionate impact on underserved and minority patients

Incidence
~2.5% of infants experience hypersensitivity reactions to cow’s milk in their 1st year of life (1)[B].

Prevalence

  • The prevalence of IgE-mediated food allergy assessed by food challenge is 3% (1)[B].
  • The self-reported prevalence of food allergy is 12% in children and 13% in adults (1)[B].
  • In young children, the most common food allergies are cow’s milk (2.5%), egg (1.3%), peanut (0.8%), and wheat (0.4%) (2)[B].
  • Adults more commonly have allergies to shellfish (2%), peanuts (0.6%), tree nuts (0.5%), and fish (0.4%).
  • Food allergy is frequently a transient phenomenon; only 3–4% of children >4 years of age have persisting food allergy (2)[B].
  • 20% of children with peanut protein allergy may outgrow their sensitivity by school age.

Etiology and Pathophysiology

Allergic response triggered by immunologic mechanisms (e.g., IgE-mediated or non–IgE-mediated allergic responses) or non–immunologic-mediated mechanisms

  • Any ingested substance can cause allergic reactions:
    • Most commonly implicated foods include cow’s milk, egg whites, wheat, soy, peanuts, fish, tree nuts (e.g., walnut, cashew, and pecan), and shellfish.
  • Several food dyes and additives may elicit non–IgE-mediated allergic-like reactions.

Genetics

  • Although there is likely a heritable component to allergic diseases, the genetics are complex and not monogenic.
  • Human leukocyte antigen (HLA) studies in peanut allergy have consistently failed to find associations.
  • In families with a history of food hypersensitivity, the probability of food allergy in subsequent siblings may be as high as 50%.

Risk Factors

  • Patients with allergic or atopic predisposition have increased risk of hypersensitivity reaction to food.
  • Family history of food hypersensitivity

General Prevention

  • High-risk infants fed peanut protein (6 g/week) have an 80% risk reduction in developing peanut allergy by age 5 years, and global infant feeding guidelines now recommend introducing peanut and other complementary foods starting at 5 months of age.
  • In patients at risk for anaphylaxis, epinephrine autoinjectors should be readily available.

Commonly Associated Conditions

  • Atopic dermatitis
  • Eosinophilic esophagitis

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Basics

Food allergy is defined as an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.

Description

  • Hypersensitivity reaction related to certain food exposures; can involve IgE-mediated and non–IgE-mediated mechanisms
  • System(s) affected: gastrointestinal (GI), heme/lymphatic/immunologic, pulmonary, skin/exocrine
  • Synonym(s): allergic bowel disease; dietary protein sensitivity syndrome

Epidemiology

  • Predominant age: all ages but more common in infants and children
  • Predominant sex: male > female (2:1)
  • Disproportionate impact on underserved and minority patients

Incidence
~2.5% of infants experience hypersensitivity reactions to cow’s milk in their 1st year of life (1)[B].

Prevalence

  • The prevalence of IgE-mediated food allergy assessed by food challenge is 3% (1)[B].
  • The self-reported prevalence of food allergy is 12% in children and 13% in adults (1)[B].
  • In young children, the most common food allergies are cow’s milk (2.5%), egg (1.3%), peanut (0.8%), and wheat (0.4%) (2)[B].
  • Adults more commonly have allergies to shellfish (2%), peanuts (0.6%), tree nuts (0.5%), and fish (0.4%).
  • Food allergy is frequently a transient phenomenon; only 3–4% of children >4 years of age have persisting food allergy (2)[B].
  • 20% of children with peanut protein allergy may outgrow their sensitivity by school age.

Etiology and Pathophysiology

Allergic response triggered by immunologic mechanisms (e.g., IgE-mediated or non–IgE-mediated allergic responses) or non–immunologic-mediated mechanisms

  • Any ingested substance can cause allergic reactions:
    • Most commonly implicated foods include cow’s milk, egg whites, wheat, soy, peanuts, fish, tree nuts (e.g., walnut, cashew, and pecan), and shellfish.
  • Several food dyes and additives may elicit non–IgE-mediated allergic-like reactions.

Genetics

  • Although there is likely a heritable component to allergic diseases, the genetics are complex and not monogenic.
  • Human leukocyte antigen (HLA) studies in peanut allergy have consistently failed to find associations.
  • In families with a history of food hypersensitivity, the probability of food allergy in subsequent siblings may be as high as 50%.

Risk Factors

  • Patients with allergic or atopic predisposition have increased risk of hypersensitivity reaction to food.
  • Family history of food hypersensitivity

General Prevention

  • High-risk infants fed peanut protein (6 g/week) have an 80% risk reduction in developing peanut allergy by age 5 years, and global infant feeding guidelines now recommend introducing peanut and other complementary foods starting at 5 months of age.
  • In patients at risk for anaphylaxis, epinephrine autoinjectors should be readily available.

Commonly Associated Conditions

  • Atopic dermatitis
  • Eosinophilic esophagitis

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