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Food allergy has recently been 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:
- IgE mediated, including
- Acute urticaria
- Oral allergy syndrome
- Non–IgE mediated (cell mediated), including
- Food protein–induced enterocolitis syndrome (FPIES)
- Food protein–induced allergic proctocolitis
- Celiac disease
- Mixed IgE and non–IgE mediated, including
- Atopic dermatitis
- Eosinophilic gastroenteropathies (eosinophilic esophagitis, eosinophilic gastroenteritis)
- IgE mediated, including
- Most common IgE-mediated food allergies:
- Tree nuts
- Most common non–IgE-mediated food allergies associated with food protein enterocolitis and proctocolitis:
Food-induced anaphylaxis is the most common cause of anaphylactic reactions treated in emergency departments in the United States. The prevalence of food allergy has increased over the past 10–20 years.
- 5% of children <5 years of age, 4% of teens and adults
- Nearly 2.5% of infants have hypersensitivity reactions to cow’s milk during 1st year (½ of these cases are thought to actually represent GI diseases); outgrown by most (80%) by 5 years of age.
- 1.6% have egg allergy by 2.5 years (based on population-based studies); 66% of children outgrow egg allergy by 7 years of age.
- 0.6% of U.S. population have peanut allergy.
- 37% of children < 5 years of age with moderate to severe atopic dermatitis have a food allergy.
- 34–49% of children with food allergy have asthma.
- 33–40% of children with food allergy have allergic rhinitis.
- Fatal and near-fatal reactions are associated with uncontrolled asthma.
- Family history
- Presence of atopic dermatitis
- Other unknown factors suspected
- Oral tolerance to food proteins 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 binds to IgE antibodies, leading to degranulation of those cells and release of histamine and other chemical mediators.
- Non–IgE mediated (cell mediated): T cells react to protein-inducing proinflammatory cytokines, leading to inflammatory cell infiltrates and increased vascular permeability. These factors lead to subacute and chronic responses primarily affecting the GI tract.
- Mixed IgE and non–IgE mediated: Eosinophilic esophagitis and eosinophilic gastroenteropathy are characterized by eosinophilic infiltration of intestinal wall, occasionally reaching to serosa.
Commonly Associated Conditions
- Asthma (4-fold more likely)
- Allergic rhinitis (2.4-fold more likely)
- Other atopic diseases
- Dermatitis herpetiformis (celiac)