food allergy

Etiology

• eating food allergens: most common (90% of food allergies)
  • eggs
  • milk
  • nuts, especially peanuts*
  • fish, especially shellfish
  • soybean
  • wheat
• other
  • ~ 1.1 million people in the U.S. are allergic to sesame
  • cross-sensitivity between latex, banana, avocado, kiwifruit, chestnut, potato, green pepper & other fruits & nuts
  • some food allergens may be heat-labile

* Children generally outgrow allergies to milk & eggs, but NOT to peanuts. Initial sensitization to peanuts may occur by touching peanuts. Most children with peanut allergies accidentally ingest peanuts

* skin contact with food allergen produces local reaction or none at all

* proximity to someone consuming food allergen not a risk

Epidemiology

• self-reported food allergy more common than proven food allergy
• 11% of US adults have a food allergy, whereas ~ 19% of US adults believe that they have a food allergy
• food allergy is more common in children than adults
• among children, food allergy is more common in those with other atopic diseases (atopic dermatitis, asthma, allergic rhinitis)
• accidental food exposures frequently cause allergic reactions in preschool-aged children
• lower-income families have less access to support needed to prevent & treat food allergy complications, resulting in preventable emergency department visits & hospitalizations

Clinical manifestations

• IgE-mediated cutaneous reactions
  • acute urticaria (common), almost never chronic urticaria
  • flushing, pruritus
  • angioedema & anaphylaxis may occur
• cell-mediated cutaneous reactions
  • contact dermatitis
  • dermatitis herpetiformis
• mixed cutaneous reactions
  • atopic dermatitis
• other
  • tingling, itching or metallic taste may occur while food is still in the mouth
  • within 15 minutes after swallowing the food, epigastric distress should occur
  • nausea/vomiting
  • lower abdominal cramping
  • diarrhea
  • wheezing

Laboratory

• screening with serum IgE testing not indicated
• low levels of serum allergen (food)-specific IgE have low predictive value
• see ARUP consult

Diagnostic procedures

• sensitive but non-specific testing
  • skin testing for food allergens
    • skin prick testing
      • high sensitivity, moderate specificity
      • initial test of choice for food allergens
    • intradermal skin testing
      • may result in false positives
      • may trigger severe reactions if food allergens are injected
  • in vitro testing for specific IgE
  • reserve for patients with positive skin test or IgE but without convincing history
  • avoid food allergy panel testing
  • check for allergies only to implicated foods
  • focus on most common foods implicated in food allergies (see etiology)
• double-blind food challenge test is the standard test
  • end points are nausea/vomiting, diarrhea, abdominal cramps
  • potentially dangerous test

Management

• avoid offending food
• epinephrine is 1st line treatment for all instances of anaphylaxis
• antihistamines
• glucocorticoids
• patients with history of anaphylaxis to food should carry epinephrine kit (prescription for 2 doses)
• activated charcoal may interfere with absorption of antihistamines & steroids
• anti-IgE therapy appears to confer protection against peanut reactions in some patients
• prevention
  • no medications or allergen-specific immunotherapies are recommended to prevent an allergic reaction
  • for infants with a family history or atopy, consider partially or extensively hydrolyzed infant formula to prevent atopic dermatitis
  • immunotherapy
    • omalizumab injections for 16 weeks, begun 8 weeks prior to oral immunotherapy with up to 5 allergens
    • omalizumab FDA-approved for reducing allergic reactions to foods
    • omalizumab increases threshold for reaction to peanuts & other common food allergens
  • no evidence to support avoidance of foods with additives for chronic idiopathic urticaria
  • not necessary to avoid all tree nuts in people with a single tree nut allergy
  • introduction of allergenic foods at 3 months of age vs after 6 months of age in breast-fed infnats associated with lower prevalence of food allergy at 1-2 years of age (2.4 vs 7.3%)
  • introducing infants to egg at ages 4-6 months & to peanut at ages 4-11 months is associated with reduced risk for egg allergy & peanut allergy

More general terms

• type 1 hypersensitivity; immediate hypersensitivity (allergy)
• food intolerance

More specific terms

• cow's milk hypersensitivity (CMH); cow's milk allergy
• egg allergy
• multiple food allergies
• peanut allergy
• pollen-food allergy syndrome
• seafood allergy (include shellfish allergy)

Additional terms

• angioneurotic edema; angioedema; atrophedema; Bannister's disease; Milton's disease; Quincke's disease; periodic or Quincke's edema; giant urticaria or hives; urticaria gigans, gigantea, or tuberosa.
• food poisoning (foodborne disease)
• insect sting or anaphylaxis kit (Ana-Kit)
• urticaria (hives)

Patient information

food allergy patient information