early introduction of peanut reduces peanut allergies

Introduction 

Symptoms such as hives, vomiting and wheezing can signal a possible food allergy. These symptoms result from an immune reaction mediated by the ingestion of a particular food. This reaction is reproducible with every consumption of the offending food. Specific testing to the offending food validates the cause of these symptoms. The prevalence of food-based reactions has been increasing over the past decade. This rapid rise in food allergies has prompted a widespread effort to discover, and possibly prevent, the etiology.  

In 2000, the American Academy of Pediatrics (AAP), based on expert opinion, recommended that infants who were at risk for food allergy avoid the introduction of milk until 1 year of age, eggs until 2 years of age and nuts and fish until 3 years of age.₁ From 1997 to 2008, the prevalence of peanut allergy in children rose from 0.4 to 1.4 percent, while tree nut allergy increased from 0.6 to 2.1 percent.₂ In 2008, citing lack of evidence that delaying the introduction of complimentary foods decreased food allergy, the AAP reversed its earlier position.₃

Also in 2008, researchers in the United Kingdom (UK) noted as peanut allergy increased in the United States (US) and Europe, the prevalence of peanut allergy in Israeli children remained stagnant. After controlling for social factors, the rate of peanut allergy in Jewish children in Israel was one-tenth the rate of Jewish children in the UK.₄  The predominant difference between these two groups was the age at which peanut was introduced into the diet. The Jewish children in Israel consumed peanut proteins as infants due to cultural practices while Jewish children in UK did not introduce peanut until much later in life. This spawned the hypothesis that the age of peanut introduction into the diet was important for oral tolerance. This hypothesis would be tested in the Learning Early About Peanut Allergy (LEAP) study. 

LEAP Study

The LEAP study, published in the New England Journal of Medicine in 2015, greatly furthered our knowledge regarding dietary peanut introduction and its role in peanut allergy prevention. This study randomized 640 infants between the age of 4 to 11 months with a history of severe eczema and/or egg allergy either to peanut consumption or to peanut avoidance. Skin prick to peanut at baseline determined ability for inclusion and only those less than 4 mm were included. At age 60 months, oral food challenge determined the rate of peanut allergy in the two groups. Among the participants who were initially skin prick negative, the prevalence of peanut allergy was 13.7 percent in the peanut avoidance group and 1.9 percent in the peanut consumption group, a relative risk reduction of 86 percent. Among participants who were skin prick positive (1 to 4 mm), the prevalence of peanut allergy was 35.3 percent in the peanut avoidance group and 10.6 percent in the peanut consumption group, a relative risk reduction of 80 percent.₅ This study suggested that early introduction of peanut protein may prevent peanut allergy.

Since the publication of this landmark trial, discussions regarding the implementation of these findings into the general population have been the subject of multiple articles. In January 2017, an expert panel from the National Institute of Allergy and Infectious Diseases (NIAID) produced an Addendum Guideline for the Prevention of Peanut Allergy to accomplish this goal.  

Guideline 1₆

 The first guideline recommends, prior to peanut introduction, infants with severe eczema (see definition) or egg allergy (see definition) undergo a screening evaluation. To ensure that multiple providers could conduct screening, the expert panel recommended starting with a peanut-specific IgE level.  If this level is less than 0.35 kUA/L, there is low risk of reaction and peanut can be safely introduced at home. However, if the peanut value is > 0.35 kUA/L, then specialist evaluation should ensue (orange boxes in Figure 1). During specialist evaluation, skin prick testing (SPT) to peanut should occur. Patients are then stratified into three groups: (1) SPT is 0 to 2 mm; this group has low risk and may introduce peanut proteins at home, (2) SPT is 3 to 7 mm; this group has moderate to severe risk and peanut protein introduction should be completed under supervision, (3) SPT .8mm; these patients are likely allergic to peanut proteins and avoid peanuts unless under the supervision of a specialist (blue boxes in Figure 1). The expert panel also suggests that this evaluation is conducted at 4 to 6 months of age and that peanut proteins are introduced as soon as solids are developmentally tolerated. 

Guideline 2₆ 

The expert panel recommends no evaluation for infants with mild to moderate eczema. Peanut protein should be introduced near age 6 months to prevent peanut allergy. The infant should have the developmental capacity to tolerate ingestion of solids. Cultural practices and family preferences should dictate the introduction of peanut proteins. This recommendation is based on expert opinion, as these infants were not thoroughly studied in the LEAP trial. 

Guideline 3₆ 

Infants with no eczema or history of food allergy can have peanut proteins introduced into the diet in accordance with family preference or cultural practices. 

Conclusion 

Peanut allergy has been increasing over the past decade. The LEAP trial documented that the timing of peanut protein introduction into the diet of high-risk infants is important in subsequent development of peanut allergy. The new guidelines from the NIAID raise a multitude of questions, such as: 1) How much peanut protein must be consumed to avoid peanut allergy? 2) How long does regular consumption have to occur to avoid peanut allergy? and 3) Since peanut and peanut butter are a choking hazard to infants, how does a parent safely introduce peanut proteins at home? 

During the LEAP trial, infants consumed two grams of peanut protein three times per week. It is unknown if consumption of less peanut protein would still result in the tolerance demonstrated. Because of this lack of data, the guidelines recommend peanut protein consumption of two grams three times per week. 

After the LEAP study, many of the patients participated in the LEAP ON trial. During this trial, participants from the LEAP trial avoided peanut protein for 12 months regardless of their original peanut consumption status during LEAP. Peanut allergy did not increase significantly in the group who had initially consumed peanut and then abstained for one year.8  This suggests that infants who develop peanut tolerance after sustained consumption can stop without increasing their risk for peanut allergy. It is unknown whether stopping peanut consumption earlier would result in sustained tolerance. Because of this lack of data, it is unknown how long peanut protein consumption must continue to avoid allergy. 

Peanuts and peanut butter are a choking hazard to infants complicating the introduction of peanut proteins into their diets. The NIAID guidelines state that infants should have the developmental ability to tolerate solids prior to the introduction of peanut proteins. In the Journal of Allergy and Clinical Immunology article which discusses these recommendations, the authors suggest thinning peanut butter with hot water or making a puree with fruit.₇   This article additionally provides guidance for home challenges and can serve clinicians well with the implementations of the above guidelines.   

In 2000, the AAP recommended avoiding peanut proteins until age 3. A sudden rise in peanut allergy prompted a reversal of this recommendation. Earlier introduction of peanut proteins in high-risk infants clearly will prevent some peanut allergy in this population. However, a note of caution must be issued. These recommendations currently can only be applied to peanut proteins. It is not clear, with respect to other allergens, whether early introduction is beneficial. With the new peanut guidelines, the NIAID hopes to influence the prevalence of peanut allergy on a population level. With our help, the prevalence of peanut allergy will certainly decrease.   

earn CME credits

This article is part of a recent issue of Pediatric Forum, a journal for physicians by physicians. 

references 

1. Baker SS. Hypoallergenic infant formulas. Pediatrics. 2000;106(2):346-349. 

2. Sicherer SH, et al. US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow up. Journal of Allergy and Clinical Immunology. 2010;125(6):1322-1326. 

3. Greer FR, et al. Effects of early nutritional interventions on the development of atopic disease in infants and children: The role of maternal dietary restriction, breastfeeding, timing of introduction of complementary foods, and hydrolyzed formulas. Pediatrics. 2008;121(1):183-191. 

4. Du Toit G, et al. Early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy. Journal of Allergy and Clinical Immunology. 2008;122(5):984-991. 

5. Du Toit G, et al. Randomized trial of peanut consumption in infants at risk for peanut allergy. New England Journal of Medicine. 2015;372(9):803-813. 

6. National Institute of Allergy and Infectious Diseases | health information. Addendum guidelines for the prevention of peanut allergy in the United States: Summary for clinicians. https://www.niaid.nih.gov/sites/ default/files/peanut-allergy-preventio…. Published January 2017. Accessed April 2017. 

7. Togias A, et al. Addendum guidelines for the prevention of peanut allergy in the United States: Report of the National Institute of Allergy and Infectious Disease-sponsored expert panel. Journal of Allergy and Clinical Immunology. 2017;139(1):29-44. 

8. Du Toit G, et al. Effect of avoidance on peanut allergy after early peanut consumption. New England Journal