peanut allergy

Etiology

• eating peanuts or peanut products
• risk factors for peanut allergy
  • infant formulas containing soy
  • infant exposure to peanut oil containing creams

* skin contact with peanuts produces local reaction or none at all

* proximity to someone consuming peanuts not a risk

Epidemiology

• one of the most common & severe food allergies
  • prevalence is 1.3-1.6% (0.6-1.2% in children)
• 10% of people allergic to peanuts are also allergic to soy
• many children with asthma have peanut allergy but do not know it

Pathology

• allergy is mediated by antigen-specific IgE

Clinical manifestations

• see food allergy

Laboratory

• peanut IgE Ab in serum

Diagnostic procedures

• peanut allergen skin testing
  • wheal diameter <2 mm: child may try peanut at home
  • wheal diameter 3-7 mm: peanut should be administered by a supervised feeding or graded challenge
  • wheal diameter >= 8 mm: child is likely allergic, should avoid peanut & be managed by a specialist

Management

• antihistamines
• steroids
• epinephrine*
• activated charcoal may interfere with absorption of antihistamines & steroids
• monoclonal antibody to IgE may be useful for prophylaxis
• oral immunotherapy (development of tolerance)
  • oral immunotherapy consisting of incrementally increasing oral doses of peanut
    • procedure:
      • hospitalized children spent a day swallowing small but increasing doses of a specially prepared peanut flour, until they had a reaction
      • the child was sent home with a daily dose just under the reactive amount, generally ~ 1/1000 of a peanut
    • after 8-10 months of gradual dose increases, most chilren can eat the peanut-flour equivalent of 15 peanuts daily
    • oral immunotherapy may be less effective in adults than in children & adolescents
    • complications: increased risk for anaphylaxis* (RR=3.1)
  • introduction of peanuts into the diet from age 4-11 months through 5 years of age decreases development of peanut allergy in high-risk infants
  • combined probiotic (Lactobacillus rhamnosus) & peanut oral immunotherapy daily for 18 months associated with peanut tolerance in allergic children at 3 & 12 months & at least 4 years after treatment
  • Hello Peanut 1st food item with FDA-backed claim that it may prevent development of peanut allergy
  • discontinuing or lowering the dose of oral immunotherapy may lead to resensitization
• epicutaneous immunotherapy
  • patch containing 100 or 250 micrograms peanut protein changed daily
  • 46-48% of patients able to ingest >= 10 times the peanut protein he or she could at baseline
  • appears to increase peanut tolerance, but only in children

* patients with history of anaphylaxis to peanuts should carry epinephrine kit or Epipen

* epinephrine should be administered at the first sign that something is wrong while eating (see anaphylaxis)

Prevention:

• early introduction of peanut-containing foods at
  • 4 to 6 months for infants with severe eczema, egg allergy, or both
  • 6 months for infants with only mild-to-moderate eczema
• infants without eczema or any food allergy should eat solid foods containing peanuts in accordance with family preferences & cultural practices

Notes

• patients should avoid food with cumin powder or ground cumin
  • some products containing cumin have tested positive for undeclared peanut protein
• all low-risk infants can start peanut around age 6 months
• infants with severe eczema or egg allergy should be evaluated with skin testing by a specialist
• peanut IgE Ab in serum may be ordered if no specialist is readily available

More general terms

• food allergy

Additional terms

• peanut