Food Allergy

Food Allergy: Excerpt from The 5-Minute Pediatric Consult

Stephen McGeady, MDLinda Muir, MD (4th Edition)Christopher Justinich, MD (4th Edition)

Food Allergy - BASICS

Food Allergy - description

Adverse immunologic response to food proteins (Excellent discussions of cutaneous and respiratory food hypersensitivities have been published elsewhere; this topic focuses on GI aspects.)

• GI food hypersensitivity reactions classified as:
  • IgE mediated, including:
    • Anaphylaxis
    • Oral allergy syndrome
  • Non-IgE mediated (cell mediated), including:
    • Dietary protein enterocolitis
    • Proctitis and enteropathy
    • Celiac disease
  • Mixed IgE and non-IgE mediated, including:
    • Atopic dermatitis
    • Eosinophilic gastroenteropathies
• Most common food allergies:
  • Children:
    • Milk
    • Egg
    • Soy
    • Peanut
    • Wheat
    • Fish
  • Adults:
    • Peanuts
    • Tree nuts
    • Fish
    • Shellfish

Food Allergy - epidemiology

Food-induced anaphylaxis is the most common cause of anaphylactic reactions treated in emergency departments in the US.

Food Allergy - incidence

Unknown

Food Allergy - prevalence

• 5–8% of children <3 years of age
• Nearly 2.5% of infants have hypersensitivity reactions to cow’s milk during 1st year; outgrown by most (80%) by 5 years of age.
• 1.3% have egg allergy by 2.5 years (based on population-based studies).
• 37% of children with moderate to severe atopic dermatitis have a food allergy.
• ~6% of asthmatic children in a pulmonary clinic will have food-induced wheezing and may be at risk for fatal reactions.

Food Allergy - risk factors

• Genetic
• Other unknown factors suspected

Food Allergy - etiology

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; re-exposure to the food protein causes release of histamine and other chemical mediators from these cells.
• 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: Allergic gastritis and gastroenteropathy are characterized by eosinophilic infiltration of intestinal wall, occasionally reaching to serosa.
  • Thickening of bowel wall may lead to obstruction, pain, and other symptoms.
  • If serosal, ascites

Food Allergy - associated conditions

• Asthma
• Other atopic diseases
• Dermatitis herpetiformis (celiac)

Food Allergy - DIAGNOSIS

Food Allergy - signs & symptoms

Vary depending on the individual and the type of food hypersensitivity (see Table for symptoms of specific illnesses):

• IgE mediated:
  • Urticaria
  • Angioedema
  • Immediate GI reactions (emesis, cramping, etc.)
  • Oral allergy syndrome
  • Rhinitis
  • Anaphylaxis (hypotension, dysprea, dysphonia
  • Nausea, abdominal pain, colic vomiting develop within 2 hours of ingesting offending foods
  • Diarrhea: Develops within 2–6 hours
• Mixed IgE and non-IgE (cell mediated):
  • Eosinophilic gastroenteropathy:
    • Weight loss (key feature), pain, emesis, failure to thrive (FTT), anorexia
    • Some infants have large protein-losing enteropathy component causing low serum albumin and hypogammaglobulinemia.
  • Eosinophilic esophagitis:
    • Dysphagia
    • Intermittent vomiting
    • Food refusal
    • Abdominal pain
    • Irritability
    • Failure to respond to reflux medication
• Non-IgE mediated:
  • Food protein enterocolitis:
    • Profuse diarrhea
    • Shock due to fluid/electrolyte loss
  • Food protein proctocolitis: Blood in stool
  • Food protein–induced enteropathy:
  • Diarrhea, bloating, FTT

Food Allergy - physical exam

• IgE mediated:
  • Hives/angioedema
  • Wheezing/dyspnea
  • Hypotension/tachycardia
• Mixed IgE mediated, non-IgE mediated:
  • Eosinophilic esophagitis: Abdominal tenderness (variable)
  • Eosinophilic gastroenteropathy
    • Abdominal tenderness
    • Weight loss
• Cell mediated:
  • Food protein induced enterocolitis/proctocolitis:
    • Abdominal distension
    • FTT
  • Celiac disease:
    • Abdominal distension
    • FTT

Food Allergy - tests

Food Allergy - lab

Depends on clinical presentation and patient symptoms; may include:

• CBC with differential:
  • Anemia in patients with enteropathy
  • Eosinophilia in patients with eosinophilic gastritis or enteropathy
• Serum IgE: Elevated in:
  • IgE-mediated hypersensitivities
  • Some with allergic eosinophilic gastritis
• Albumin: Low with:
  • Protein-losing enteropathies associated with mixed eosinophilic gastroenterocolitis
  • Non-IgE–mediated protein enterocolitis
• Radioallergosorbent tests (RAST) of serum:
  • May be helpful in IgE-mediated illness
  • Many false positives
  • Often negative in eosinophilic esophagitis

Food Allergy - diag proced-surgery

• Biopsy of esophagus, stomach, small bowel, and colon
  • Children >1 year: High negative predictive accuracy, thereby excluding IgE-mediated food allergy
  • Children <1 year: Negative predictive accuracy is lower, ~80–85%.
  • Positive predictive accuracy is lower, ~50%.
• Patch skin testing:
  • May be used to evaluate for mixed (IgE/non-IgE–mediated) or cell-mediated sensitivities
  • Often negative in eosinophilic esophagitis
  • Standards for interpretation and methods for reliability are under development.
• Double-blinded, placebo-controlled food challenges:
  • Gold standard for diagnosis of food allergy, but impractical in many clinical settings
  • Used when probability of food allergy is low
  • May be unsafe in patients with convincing histories of severe allergic reaction and evidence of high levels of IgE antibody to the specific food
• Elimination diets:
  • Should be conducted with care
  • May lack critical nutrients
  • Oral rechallenge should be carefully planned, because a more severe reaction may ensue after a food has been temporarily removed.

Food Allergy - pathological findings

• Increased eosinophils in eosinophilic gastroenteropathy
• Loss of villi in celiac disease

Food Allergy - TREATMENT

Food Allergy - general measures

• Anaphylaxis:
  • Full monitoring of vital signs
  • Epinephrine if significant respiratory or cardiovascular symptoms: May be repeated
  • Antihistamines (diphenhydramine) may be given for milder symptoms.
  • Glucocorticoids may prevent biphasic reaction.
  • Nonanaphylactic food allergies: Severe eosinophilic gastroenteropathies
  • Inhaled steroids by mouth without spacer
  • Hydrolyzed or elemental formulas: Patients may respond to hypoallergenic formulas.
  • Older patients may require free amino acid formulas.
  • Anti-IgE (benefit unproven)
• Systemic steroids in resistant cases
• Probiotics such as lactobacillus GG may decrease hypersensitivity reactions to food antigens and diminish intestinal inflammation in patients with atopic eczema and food allergy by promoting endogenous intestinal barrier mechanisms.

Food Allergy - diet

Nonanaphylactic and anaphylactic food allergies: Removal of the offending food agent from diet

Food Allergy - medication

Food Allergy - first line

For anaphylaxis, full monitoring of vital signs, epinephrine if significant respiratory or cardiovascular symptoms: Hi-antihistamines (diphenhydramine) may be given for milder symptoms.

Food Allergy - second line

Severe eosinophilic gastroenteropathies:

• Systemic steroids
• Hydrolyzed or elemental formulas
• Anti-IgE and other forms of immunotherapy (investigational)
• Dietary restrictions

Food Allergy - FOLLOW UP

Food Allergy - disposition

Food Allergy - issues for referral

Allergy/Immunology and/or gastroenterology follow-up needed for most patients for long-term management.

Food Allergy - prognosis

• Generally good, after offending food antigens are removed from diet and adequate nutrients are ensured
• Tolerance to food allergens often develops over time.
• IgE-mediated disease may persist longer than non-IgE mediated.

Food Allergy - complications

• Food-protein allergy can cause:
  • Nausea
  • Anorexia
  • Vomiting
  • Diarrhea
  • Poor growth
  • Protein-losing enteropathy
  • Anemia
• Cutaneous food-sensitivity reactions
  • Recurrent urticaria/angioedema
  • Resistant atopic dermatitis
  • Contact dermatitis
  • Dermatitis herpetiformis
• Respiratory food-hypersensitivity reactions.
  • Rhinoconjunctivitis
  • Asthma
  • Heiner syndrome: Rare food-induced pulmonary hemosiderosis

Food Allergy/Hypersensitivity

Food Allergy - bibliography

1. Bock SA. Pediatric food allergy: Diagnostic evaluation. Pediatrics. 2003;111:1638–1644.
2. Burks W. Pediatric food allergy: Skin manifestations of food allergy. Pediatrics. 2003;111:1617–1624.
3. John MJ. Pediatric food allergy: Respiratory manifestations of food allergy. Pediatrics. 2003;111:1625–1630.
4. Sampson HA. Update on food allergy. J Allergy Clin Immunol. 2004;113:805–819.

Food Allergy - CODES

Food Allergy - icd9

• 558.3 Allergic gastroenteritis and colitis
• 693.1 Food allergy
• 995.0 Anaphylaxis

Food Allergy - PATIENT TEACHING-MED

Epinephrine self administration if anaphylaxis

Food Allergy - FAQ

• Q: What are common allergens?
• A: The most common allergens to which children are sensitive are milk, egg, soy, wheat, fish, and nuts.
• Q: Do you recommend elimination diets?
• A: Only in extreme circumstances because they can result in nutrient-deficient diets and malnutrition without identifying the offending allergen. Double-blinded food challenges are a better method for identifying the offending agent.

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Food allergies

• Back to disease: Food allergies: Introduction
• Next Book Extract About Food allergies: Surveys relating to Food allergies
• More Book Extracts: All Online Books for Food allergies

More Medical Textbooks Online about Food allergies

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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