Allergy

Peanut Allergy

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https://en.wikipedia.org/wiki/Peanut

Epidemiology

  • In the United States, the prevalence of peanut allergy in children has increased from 0.4% in 1997 to ~2% in 2010. The exact causes for this rising prevalance remain unknown.
  • However, observational data have shown that cultures in which infants consume peanut in high quantities in the first year of life have sigificantly lower rates of peanut allergy than cultures in which infants avoid peanut consumption in the first year.
  • Peanut allergy is the leading cause of food-induced anaphylaxis resulting in death.
  • Peanut allergy tends to persist into adulthood (unlike cow's milk or egg allergies, for which the majority are outgrown by 3-5 years of age).
  • Up to 20% of infants with peanut allergy can develop tolerance to their allergy, especially if IgE levels are low.  Children should be re-evaluated every 1-2 years as they get older.

Clinical Manifestations

Patients with peanut allergy are at risk of developing anaphylaxis if exposed to peanuts. Symptoms of anaphylaxis include flushing, urticaria (Figure 2), pruritus, angioedema (Figure 3), cough, wheezing,  stridor, dyspnea, abdominal cramping, vomiting, diarrhea, dizziness, and syncope. 

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Hives - https://en.wikipedia.org/wiki/Hives

Diagnosis

The diagnosis of a peanut allergy is dependent on a clear and specific history confirmed by testing. It is important to note that many reported food allergies by parents or patients may not be actual allergies, so confirmation is required to make a diagnosis. Available tests include a food challenge test, an elimination diet test, skin and laboratory tests. 

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Diagnostic Algorithm for Food Allergies

  • The recommended method for a food challenge is to perform a double-blinded placebo-controlled food challenge in which the suspected allergen is administered to the patient in a clinical setting with appropriate resuscitative equipment and signs and symptoms are observed. However, a single-blinded open challenge that demonstrates symptoms may be diagnostic if there is a clear history and confirmatory laboratory tests.
  • The absence of symptoms after elimination of peanuts and peanut products from the diet combined with a confirmed history of anaphylaxis after ingestion of peanuts is also diagnostic of a peanut allergy.
  • Skin prick tests and laboratory tests that measure IgE or allergen-specific IgE can assist in the diagnosis of peanut allergy, but are not diagnostic alone. These tests can have many false positives, but can be helpful when used in conjunction with history and the above tests.

Treatment

Elimination of foods containing peanuts and peanut products are the most appropriate treatment for peanut allergy. Injectable epinephrine, such as an EpiPen or Auvi-Q, and a written emergency plan in case of accidental ingestion should be given to children with peanut allergy, along with appropriate education on how to use the injectable epinephrine device.

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CLICK HERE for a video on how to use the injectible EPI PEN.

Patients should be aware of the biphasic nature of the reaction and they should CALL 911 OR GO TO THE EMERGENCY DEPARTMENT AFTER USE.

Families should also be counseled to keep their EpiPen on their person (or at school/work), as leaving in the car can expose it to extremes of heat and cold thus making the medication ineffective.

Furthermore, since it is an autoinjector, the EpiPen once expired should be brought to the clinic and placed in a sharps box to avoid accidental injection into the digits of trash / waste handlers.

Prevention of Peanut Allergy in Infants

  • Whereas previous clinical guidelines recommended avoidance of allergenic foods in infants at high risk for allergy, evidence from the Learning Early About Peanut Allergy (LEAP) Trial showed that peanut ingestion from early infancy is safe and effective for preventing peanut allergy in at-risk infants.
  • The LEAP Trial, conducted in the UK in 2015, was the first randomized, open-label, controlled trial to investigate the most effective strategy for preventing peanut allergy in infants at high risk for the allergy.
    • 640 infants between 4-11 months of age at high risk for peanut allergy (history of severe eczema and/or egg allergy) were enrolled
    • Participants were stratified into two cohorts based on pre-existing sensitization to peanut (determined by skin prick testing)
    • Participants within each cohort were randomized into two groups: a peanut consumption group and a peanut avoidance group until 5 years of age
    • Results:
      • ​For 542 participants who initially had negative skin test response to peanut, prevalence of peanut allergy at 5 years of age was 13.7% in the avoidance group vs. 1.9% in the consumption group (P<0.001)
      • For 98 infants who initially had positive skin test response to peanut, the prevalence of peanut allergy was 35.3% in the avoidance group vs. 10.6% in the consumption group (P=0.004)
  • Based on results from the LEAP Trial, in 2017 the National Institute of Allergy and Infectious Diseases published guidelines for early introduction of peanut (Addendum Guideline for the Prevention of Peanut Allergy in the United States) 

Screen Shot 2019-04-11 at 1.49.47 PM_1.png Addendum guidelines for the prevention of peanut allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases–sponsored expert panel. 2017

Note that for infants with severe eczema and/or egg allergy, guidelines strongly recommend evaluation for pre-existing peanut sensitization/allergy with skin prick testing to peanut and/or peanut-specific immunoglobulin E prior to introduction of peanut-containing foods.

References

  1. Sicherer SH, Sampson HA. Food allergy: Epidemiology, pathogenesis, diagnosis, and treatment. J Allergy Clin Immunol. 2014;133(2):291-307.e5. doi:10.1016/j.jaci.2013.11.020

  2. Du Toit G, Katz Y, Sasieni P, et al. Early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy. J Allergy Clin Immunol. 2008;122(5):984-991. doi:10.1016/j.jaci.2008.08.039

  3. Braganza SF. Food Allergy. Pediatr Rev. 2003;24(11):393-394. doi:10.1542/pir.24-11-393

  4. Du Toit G, Roberts G, Sayre PH, et al. Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy. N Engl J Med. 2015;372(9):803-813. doi:10.1056/NEJMoa1414850

  5. Togias A, Cooper SF, Acebal ML, et al. Addendum guidelines for the prevention of peanut allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases–sponsored expert panel. World Allergy Organ J. 2017;10(1). doi:10.1186/s40413-016-0137-9

  6. Up to Date: Peanut, Tree Nut, and Seed Allergy – Clinical Features (http://www.uptodate.com.proxy.uchicago.edu/contents/peanut-tree-nut-and-...)

  7. Pediatrics in Review: Anaphylaxis, Urticaria, and Angioedema, 2013 (http://pedsinreview.aappublications.org.proxy.uchicago.edu/content/34/6/...)

  8. American Academy of Family Physicians: Summary of the NIAID-Sponsored Food Allergy Guidelines, 2012 (http://www.aafp.org/afp/2011/1115/p1111.html)

  9. American Academy of Family Physicians: Anaphylaxis, Recognition and Management, 2011 (http://www.aafp.org/afp/2012/0701/p43.html)