Food allergy is defined as an adverse health effect 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 review focuses on IgE-mediated food allergies.
- A reproducible hypersensitivity reaction related to certain food exposures mediated by IgE
- System(s) affected: gastrointestinal (GI), hematologic/lymphatic/immunologic, pulmonary, skin/exocrine, cardiovascular
- Synonym(s): IgE-mediated food reactions, food hypersensitivity, anaphylaxis
- Predominant age: all ages; traditionally thought to affect infants and young children more commonly; however, recent data show increasing prevalence in adults (1).
- Predominant sex: male > female in children, female > male in adults
- Although it is difficult to discern the exact effects of socioeconomic and racial differences on food allergy prevalence, disproportionate impact on underserved and minority patients have been reported (2),(3).
Egg allergy incidence has been reported as 1.23% in infants, whereas this number for cow’s milk allergy was 0.54%.
- The prevalence of IgE-mediated food allergy assessed by food challenge, the diagnostic gold-standard, is 3%.
- The self-reported prevalence of food allergy is >10%, with 1 in 10 adults and 1 in 12 children being affected (1).
- 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%) (4).
- 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 will outgrow their milk and egg allergy, but only 20% of children with peanut allergy may outgrow their sensitivity by school age.
Etiology and Pathophysiology
- Food allergic reactions are a result of failure of immunologic tolerance to food proteins and result in immune-mediated responses to specific foods.
- 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, cashew, and pecan), fish, and shellfish. Food dyes and additives are rare causes of allergy.
- HLA alleles have been identified as genetic determinants for peanut allergy.
- Food allergy screening is currently not recommended for siblings of food allergy patients.
- 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
- High-risk infants fed peanut protein (6 g/week) have an 80% risk reduction in developing peanut allergy by the age of 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
- Atopic dermatitis; eosinophilic esophagitis
- Food protein-induced enterocolitis syndrome (FPIES); asthma; allergic rhinitis
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