2018-19 TOW #29: Food allergy

Next week’s topic is on food allergies, a hot topic with the recently evolving literature and recommendations.

Materials for next week:

A few take-home points:

  1. What’s the epidemiology? As many as 1 in 13 children is thought to have a food allergy. Along with other allergies, the rate of rise of food allergies has been rapid. While well-meaning, the recommendation to delay introduction of foods probably led to an increase in allergy development as children were sensitized through exposure, such as through the skin. Generally, the most common allergens in childhood include egg, milk, peanut, tree nuts, wheat, soy, fish, shellfish,and sesame.
  2. How do we prevent food allergies? We’ve had a recent dramatic change in practice in solid food introduction: we are now recommending solids foods between 4-6 months to “teach the body” during the window of time when less reaction occurs. We should recommend introducing a variety of foods, including foods containing peanuts, eggs, and tree nuts soon after children start solids. Mixing a bit of water into peanut butter to make it soupy is one way to expose infants to peanut butter (more recipes/options in the appendices here). For eggs, baking them into foods denatures the proteins so may be the best initial exposure for babies with a higher food allergy risk based on family history. Also egg yolks are less allergenic than egg whites. Breastfeeding for at least 4 months and when new foods are introduced is associated with decreased risk of atopy, though doesn’t necessarily prevent food allergies.
  3. How do we diagnose food allergies? Symptom reaction to the food: usually these are Type-1 IgE-mediated hypersensitivity reactions that happen within minutes of ingestion: including skin (most common), oral or nasal mucosa, GI, or respiratory reactions, or a combination of these in full anaphylaxis. Typically symptoms resolve within 4-12 hours. There are also Type-4 cell-mediated hypersensitivity reactions to food, such as milk protein allergy, that cause mostly GI symptoms. Some children avoid foods due to symptoms, so pay attention to these behaviors. Once a reaction has occurred, testing may help evaluate the allergy but are not fully diagnostic. A skin-prick test for food is recommended but it’s not 100% specific, with high false positive rate. Serum specific IgE testing is useful for patients who cannot discontinue antihistamine therapy or for those with extensive skin disease or dermatographism. An oral food challenge is considered the gold standard and may be part of making the diagnosis when it’s in question.
  4. How do we manage food allergies? Strict avoidance of the allergenic food is the primary approach. Egg and milk may be tolerated in cooked forms, with exposure helping build tolerance to other forms of the foods. Treatments for allergies are evolving and it’s exciting to see emergence of more success with new immunotherapies.
  5. How do we treat reactions and prevent death from anaphylaxis? Food-induced anaphylaxis is a “rapidly progressive, multiorgan allergic reaction that can result in death.” Recognition and quick response is essential to save lives. Anaphylaxis symptoms may be uniphasic, biphasic, or protracted. In all cases, most important is rapid treatment with IM epinephrine. Repeated epinephrine dosing should be used when symptoms progress or response is not optimal. All patients with any moderate to severe IgE-mediated reactions to foods should have self-administered IM epinephrine available. Mild skin-only reactions may be treated with diphenhydramine.

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