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Peanuts redux: following up on infant peanut exposure

We previously covered a major trial that suggested peanut avoidance was a bad idea for infants at risk of allergy. The researchers continued with those study subjects up to age 6, to see if the results still apply

Study under review: Effect of Avoidance on Peanut Allergy after Early Peanut Consumption

Introduction

Despite an increase in the number of women avoiding peanuts and other common allergy triggers during pregnancy and breastfeeding, the prevalence of peanut allergies actually increased[1] since 1997. About 4.4 million people[1] in the U.S. now have allergies to peanuts, and peanut allergies remain[2] one of the deadliest food allergies.

Figure 1 shows the general mechanism for peanuts causing allergy. There are multiple potential allergenic proteins in the peanut, all denoted by ‘ara h’ (a shortened version of the scientific name for the peanut, Arachis hypogea). Ara h1-h3[3] are linked to more severe anaphylaxis reactions, especially Ara h2. These reactions include swelling of the face and mouth, decreased blood pressure, difficulty breathing, and cardiac arrest. Development of allergies to other Ara h proteins results in less severe symptoms, like hives, gastrointestinal distress, and an itchy mouth.

Figure 1: How peanuts cause allergic reactions

Adapted from: Burks, W. J Clin Invest. 2003 Apr 1.

If you didn’t read it already, go check out “Going nuts over peanut exposure” in NERD #7 (May 2015) - the summary discussed the results of the five-year Learning Early About Peanut Allergy (LEAP) trial[4]. In short: infants at risk for developing peanut allergies who avoided peanut consumption were five times as likely to actually develop the allergy, compared to infants who consumed a peanut product at least three times per week. The infants who avoided peanuts also had higher levels of antigen markers that are characteristic of allergy development (IgE) and lower levels of antigen markers that are characteristic of immune tolerance (IgG4).

As noted in the previous NERD, a planned follow-up study would continue to evaluate members of both groups of trial participants through an additional year of peanut avoidance. When the researchers conducted the original trial, they didn’t know if the four-year early exposure would turn off the allergy development, or if it had simply suppressed it during that trial period. They wanted to determine whether continuous lifelong exposure to peanuts would be required in order to maintain tolerance, or if the early exposure effects might persist - this would be important for parents to know whether they needed to continue to be vigilant about monitoring their child’s exposure or not. This study, Persistence to Oral Tolerance to Peanut (LEAP-On) reports the data of that additional follow-up year.

Peanut allergies are one of the most common causes of allergy-related deaths, predominantly due to allergies to the peanut protein Ara h2. After conducting a previous trial that evaluated peanut consumption versus peanut avoidance in the development of peanut allergies in at risk children, the researchers continued to follow participants through an additional 12-month period of peanut avoidance to determine if the effects persisted.

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