Peanut Allergy: New Advances and Ongoing Controversies Elissa M
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Peanut Allergy: New Advances and Ongoing Controversies Elissa M. Abrams, MD,a Edmond S. Chan, MD,b Scott Sicherer, MDc Peanut allergy is one of the most common food allergies in children, with abstract increasing prevalence over time. The dual-allergen exposure hypothesis now supports transcutaneous sensitization to peanut as a likely pathophysiologic mechanism for peanut allergy development. As a result, there is emerging evidence that early peanut introduction has a role in peanut allergy prevention. Current first-line diagnostic tests for peanut allergy have limited specificity, which may be enhanced with emerging tools such as component- resolved diagnostics. Although management of peanut allergy includes avoidance and carrying an epinephrine autoinjector, risk of fatal anaphylaxis is extremely low, and there is minimal risk related to cutaneous or inhalational exposure. Quality of life in children with peanut allergy requires significant focus. Moving forward, oral and epicutaneous immunotherapy are emerging and exciting tools that may have a role to play in desensitization to aSection of Allergy and Clinical Immunology, Department of peanut. Pediatrics, University of Manitoba, Winnipeg, Manitoba, Canada; bDivision of Allergy and Immunology, Department of Pediatrics, University of British Columbia and British Columbia Children’s Hospital, Vancouver, British Columbia, Canada; and cDivision of Allergy and Immunology, Peanut allergy is one of the most family member who is peanut Department of Pediatrics, Jaffe Food Allergy Institute, Icahn School of Medicine at Mount Sinai, New York, New York common food allergies in childhood, allergic,3,4 and genetic polymorphisms with a dramatic increase over the are increasingly being linked to the Dr Abrams conceptualized and designed the article, past few decades in various parts of development of peanut allergy.5 drafted the manuscript, and revised the manuscript; 1 Drs Chan and Sicherer conceptualized and designed the Western world. Currently, Although studies vary, heritability of the article and reviewed and revised the manuscript; peanut allergy is thought to affect peanut allergy has been estimated at up and all authors approved the final manuscript as 1% to 3% of children.1 Peanut allergy to 81.6%.3 There are racial differences submitted and agree to be accountable for all is often lifelong and carries associated with the prevalence of aspects of the work. a significant daily burden that peanut allergy, although studies differ DOI: https://doi.org/10.1542/peds.2019-2102 2 adversely affects quality of life (QoL). in results, and boys appear more likely Accepted for publication Aug 21, 2019 6 As a result, prevention of peanut to develop peanut allergy than girls. Address correspondence to Elissa M. Abrams, MD, allergy, as well as accurate diagnosis Section of Allergy and Clinical Immunology, and management of peanut allergy, is Studies have supported a role for Department of Pediatrics, University of Manitoba, essential. Our goal for this narrative vitamin D deficiency and hygiene in the FE125-685 William Ave, Winnipeg, MB R2M 5L9, review is to discuss the latest development of peanut allergy. For Canada. E-mail: [email protected] evidence about peanut allergy example, an observational study of PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, prevention as well as advances and 5276 1-year-old infants in Australia 1098-4275). ongoing controversies in peanut allergy found that vitamin D insufficiency Copyright © 2020 by the American Academy of diagnosis, management, and therapy. increased the risk of peanut allergy 11- Pediatrics fold.7 Higher latitudes have been FINANCIAL DISCLOSURE: The authors have indicated associated with higher rates of both they have no financial relationships relevant to this article to disclose. MECHANISMS UNDERLYING THE food allergy and anaphylaxis.8 It is DEVELOPMENT OF PEANUT ALLERGY FUNDING: thought that with increased hygiene No external funding. There are genetic and environmental (and hence, decreased microbial contributors to the development of exposure) there are altered To cite: Abrams EM, Chan ES, Sicherer S. Peanut peanut allergy. Peanut allergy is more immunoregulatory responses that skew Allergy: New Advances and Ongoing Controversies. Pediatrics. 2020;145(5):e20192102 common in children with an immediate toward an allergic response.9 Downloaded from www.aappublications.org/news by guest on September 30, 2021 PEDIATRICS Volume 145, number 5, May 2020:e20192102 STATE-OF-THE-ART REVIEW ARTICLE An exciting development in to be due to inherent genetic 11 months of age) reduces the risk of understanding the causal susceptibility, has more recently been peanut allergy (P = .009).20 mechanisms of peanut allergy is the shown to be, at least partly, related to After publication of the LEAP study, proposal of the dual-allergen the environmental effect of avoidance an expert panel convened by the exposure hypothesis, which of peanuts in siblings of children with National Institute of Allergy and postulates that allergic sensitization peanut allergy.4,15,16 Infectious Diseases released to peanut (as well as other allergenic a guideline on the prevention of foods) occurs through cutaneous peanut allergy in the United States exposure, especially in children with PEANUT ALLERGY PREVENTION recommending that in infants with an impaired skin barrier such as severe eczema and/or egg allergy, atopic dermatitis.9,10 In contrast, In the past several years, in keeping infant-safe forms of peanut should be ingestion of allergenic foods (oral or with the dual-allergen exposure introduced as early as 4 to 6 months gastrointestinal exposure) promotes hypothesis, evidence has emerged of age after peanut allergy screening immune tolerance.9 that early ingestion of peanut has tests.21 The guideline defines severe a role in the prevention of peanut Mutations of the FLG gene (FLG is eczema as “persistent or frequently allergy. In 2008, an observational involved in skin-barrier integrity and recurring eczema with typical study revealed a 10-fold higher water retention) have been linked morphology and distribution prevalence of peanut allergy among with atopic dermatitis assessed as severe by a health care Jewish school-aged children in the development,11 with null FLG alleles provider and requiring frequent need United Kingdom compared with associated with early, persistent for prescription-strength topical Jewish school-aged children in Israel atopic dermatitis as well as increased corticosteroids, calcineurin inhibitors, (P , .001), with the major difference risk of other atopic conditions, or other anti-inflammatory agents between the populations being age at including food allergy.12 In addition, despite appropriate use of introduction of peanuts.17 Peanut was an association between atopic emollients.” This guideline introduced more commonly in the dermatitis, peanut exposure, and recommends that infants with mild first year of life and fed more peanut allergy has been documented eczema receive peanut at ∼6 months regularly as part of the diet in Israel in multiple large studies. For example, of age. Other international guidance than in the United Kingdom. In 2015, a birth cohort study of 13 971 has followed suit, suggesting that the Learning Early About Peanut children revealed that application of peanut be introduced, or not delayed, Allergy (LEAP) trial, a randomized peanut oil–containing creams onto in higher-risk infants between 4 and controlled trial of 640 infants at risk the surface of infants with atopic 6 months of age, although the for peanut allergy due to severe dermatitis was significantly definition of an infant at high risk eczema and/or egg allergy, provided – associated with the development of varies between guidelines.22 24 high-level evidence that early peanut allergy (odds ratio 6.8; 95% ingestion of peanut (between 4 and Some uncertainties about the role of confidence interval [CI]: 1.4–32.9).13 11 months of age) reduced peanut early peanut ingestion as a means of In contrast, no association was noted allergy by up to 80% compared with allergy prevention remain. The between the development of peanut peanut avoidance until 5 years of necessary amount of peanut ingested, allergy and the use of creams not age.18 A strong protective effect with as well as the required frequency of containing peanut oil (because the oil early peanut introduction was seen in peanut ingestion, is not known. The was not placed on the eczematous infants with both negative and mildly benefit of early ingestion in lower- skin of the infant) or the use of breast positive results on the peanut skin risk infants is also uncertain. It creams containing peanut oil. Of prick test (SPT), suggesting a primary remains controversial whether high- those children who became peanut and secondary preventive effect. In risk infants should have screening allergic, 84% (P , .001) had been a follow-up study to LEAP (LEAP-On), SPTs to peanut or serum peanut- exposed to peanut oil–containing 1 year of peanut avoidance after specific immunoglobulin E (IgE) creams in the first 6 months of life. 5 years of age did not increase the testing before peanut introduction, Finally, there is an intricate risk of peanut allergy between groups and screening criteria may be interaction between genetic and (P = .25), suggesting longevity of this susceptible to a variety of pitfalls, environmental factors such as protective effect.19 A recent meta- including high false-positive rates and delayed ingestion of peanut.