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Food Allergies, Part 1

Torie Grant, MD MHS and Neda Frayha, MD
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Sometimes it can seem like every other child we see has a food allergy. How prevalent are food allergies in the general population, and how can we best diagnose and manage them? To shed light on these questions, as well as recent guideline changes in the allergy community and novel therapies on the horizon, PC RAP welcomes back Dr. Torie Grant, a Med/Peds allergist and immunologist at Johns Hopkins. She sits down with Neda to share the full scoop on food allergies.

 

Pearls:

  • If you do send a large panel of allergy testing, do not take out food from the child’s diet if they are tolerating that food. That can actually end up sensitizing them to the food and lead to a new food allergy.

  • Fatality is rare with food allergies but is most often associated with a delay in administration of epinephrine. If you are concerned, give epinephrine because antihistamines and steroids alone will not cut it.

  • Emerging treatments include a peanut patch and oral immunotherapy. These are NOT cures but designed to help with small amounts of exposure from cross-contamination.

 

  • Background:

    • Definitions:

      • Allergy - involves mast cells that release histamine, leukotriene and other types of allergy mediators that lead to symptoms if the allergen is consumed AND is often confirmed with skin prick testing or blood IgE testing.

        • Pearl: negative predictive value of allergy testing is 97% while the positive predictive value is only 50% (meaning, people may test positive for it but not actually have an allergic reaction)

    • Affects 1 in 6 children in the western hemisphere, 6 million children in the US

    • Allergies are on the rise for hypothesized reasons:

      • Improvement in hygiene so we have fewer exposure to microbes/bacteria

      • We are feeding babies less of the food adults eat

    • Specific allergies on the rise: milk, egg, peanut, tree nuts (almonds, cashews, pistachios, hazelnuts, pecans, walnuts, pine nuts, macademia nuts), wheat, fish, shellfish and soy

      • Pearl: Toughest allergies to outgrow are nut allergies, fish and shellfish. Half of kids will outgrow milk, egg and wheat allergy by about age 5.

  • History:

    • What exactly did you eat?

    • When was the onset of symptoms?

    • What were the symptoms?

      • Hives, flushing, lip swelling, trouble breathing, sheezing, runny nose, congestion, dizziness, lightheadedness

    • Is this the first time you ate the food?

    • Do you ever NOT have symptoms when you eat this food?

      • A difference  between food sensitivity or intolerance and allergy is that you have the reaction every time with a true allergy

  • Allergy testing:

    • Allergy testing can lead to harm. For example, if a child who may have a propensity for an egg allergy (but is not allergic and eats eggs without issue) gets tested. The test comes back weakly positive so they are told to stop eating eggs. Three months pass until they see the allergist who retests and finds their numbers have shot up. By removing the eggs from the diet, that child can be pushed into developing an egg allergy. Had they continued to eat eggs, they may have just outgrown it or never developed the allergy in the first place!

    • Pearl: negative predictive value of allergy testing is 97% while the positive predictive value is only 50% (meaning, people may test positive for it but not actually have an allergic reaction). Atopic conditions can lead to low levels of IgE to allergens that do not result in a true allergy.

    • Order an allergy test for a specific allergen of concern as opposed to an entire panel or get to an allergist (if available) to let them handle testing

  • Recent updates in guidelines and the literature:

    • Learning Early About Peanut (LEAP) in 2015 showed early introduction to peanut allergy was protective against developing a peanut allergy

      • Took infants age 4-11 months in the UK who had atopic predisposition (moderate to severe eczema, egg allergy or both)

      • Skin prick test for peanut had to be negative

      • Randomized to either avoid peanuts strictly or introduce peanut on a relatively frequent basis (1-3 times per week)

      • Kids who avoided peanuts had peanut allergy 35% v. 10% in those who introduced peanuts → 70% relative risk reduction

      • Follow-up study (LEAP-On) showed the effect was lasting

    • Early Introduction of Allergenic Foods (EAT) study

      • Took all infants starting at 3 months and pushed 6 foods (milk, egg, peanut, sesame, wheat, fish) until age 3

      • Found no difference in breastfeeding duration and no difference in allergies to these foods

    • HealthNut Study in Australia

      • Cohort of 5200 kids

      • Infants who got whole egg (not baked into things) had lower incidence of egg allergy at age one

    • AAP 2017 guidelines

      • Becoming increasingly less restrictive about allergen introduction

      • Recommend earlier introduction of peanut products in particular for kids:

        • Kids with severe eczema egg allergy or both - evaluation with IgE or skin prick test or oral food challenge at 4-6 months

        • Kids with mild to moderate eczema - introduce peanut-containing foods at 6 months

        • Kids with no eczema or allergy - introduce when age-appropriate

      • Bottomline: No food restrictions during pregnancy, no food restrictions during breastfeeding unless evidence of a food reaction and parents can introduce solids at 4-6 months without restriction (unless evidence of food reaction)

  • Management:

    • IgE testing for the specific allergens in question

    • Injectable epinephrine  if concerned about a severe reaction like anaphylaxis

    • Counseling to avoid the food because even if the initial reaction is hives, they may end up having an anaphylactic reaction

    • Referral to allergist

      • May see at least annually to follow skin test or IgE levels because patient may outgrow it and tolerate an oral challenge

    • Acute management if you have eaten an allergen:

      • Mild (itching in mouth, runny nose, hive or two) → fast-acting antihistamine like diphenhydramine or cetirizine, observation

      • Progression of symptoms → injectable epinephrine → call 911 or go to the nearest emergency room

  • Emerging therapies:

    • Peanut patch worn transdermally and peanut oral immunotherapy are designed to protect against small levels of cross-contamination NOT cure a peanut allergy

  • Tips for families:

    • Parents should read labels

    • Avoid foods that have cross contamination labels

      • Roughly 5% of those foods may have some level of that protein

      • Roughly 2.5% of those foods may contain a level high enough that somebody may react

    • Good resources for parents:

      • FARE (Food Allergy Research Education) has tips about reading labels, eating out, travel

 

REFERENCES: 

  1. Bellach J, Schwarz V, et al. Randomized placebo-controlled trial of hen’s egg consumption for primary prevention in infants. J Allergy Clin Immunol 2017; 139(5):1591-1599. 

  2. DuToit G, Roberts G, Sayre PH, et al for the LEAP Study Team. Randomized trial of peanut consumption in infants at risk for peanut allergy. N Engl J Med 2015; 372:802-813.

  3. DuToit G, Roberts G, Sayre PH, et al for the Immune Tolerance Network LEAP-ON Study Team. Effect of avoidance on peanut allergy after early peanut consumption. N Engl J Med 2016; 374:1435-1443. 

  4. Keet CA, Savage JH, et al. Temporal trends and racial/ethnic disparity in self-reported pediatric food allergy in the United States. Ann Allergy Asthma Immunol 2014; 112(3):222-229.e3

  5. Lack G. Update on risk factors for food allergy. J All Clin Immunol 2012; 129(5):1187-1197.

  6. Natsume O, Kabashima S, et al. Two-step egg introduction for prevention of egg allergy in high-risk infants with eczema (PETIT): a randomised, double-blind, placebo-controlled trial. Lancet 2017; 389(10066):276-286.

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Primary Care RAP Written Summary April 2020 1 MB - PDF

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