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The fact that genetic and environmental factors could trigger disruption of the epithelial barrier and subsequently initiate a T H 2 inflammatory cascade conversely proposes that protecting the same barrier and promoting adequate interactions with other organs, such as the gut, may be crucial for lowering the risk and preventing atopic diseases, particularly, food allergies. In this review, we provide an overview of structural characteristics that support the epithelial barrier hypothesis in patients with atopic dermatitis, including the most relevant filaggrin gene mutations, the recent discovery of the role of the transient receptor potential vanilloid 1, and the role involvement of the microbiome in healthy and damaged skin. We present experimental and human studies that support the mechanisms of allergen penetration, particularly the dual allergen exposure and the outside-in, inside-out, and outside-inside-outside hypotheses. We discuss classic skin-targeted therapies for food allergy prevention, including moisturizers, steroids, and topical calcineurin inhibitors, along with pioneering trials proposed to change their current use (Prevention of Allergy via Cutaneous Intervention and Stopping Eczema and ALlergy). We provide an overview of the novel therapies that enhance the skin barrier, such as probiotics and prebiotics topical application, read-through drugs, direct and indirect FLG replacement, and interleukin and janus kinases inhibitors. Last, we discuss the newer strategies for preventing and treating food allergies in the form of epicutaneous immunotherapy and the experimental use of single-dose of adeno-associated virus vector gene immunotherapy., Competing Interests: Disclosures Dr Ciaccio receives research grant support from the National Institutes of Health (NIH), Food Allergy Research & Education (FARE), and Paul and Mary Yovovich and has served as a medical consultant/advisor for Genentech, Novartis, Siolta, Clostrabio, and FARE. Dr Chinthrajah reports receiving grants from National Institute of Allergy and Infectious Diseases (NIAID), CoFAR, Regeneron, Stanford Maternal and Child Health Research Institute, and FARE and is an advisory board member at Alladapt Therapeutics, Novartis, Genentech, Allergenis, Intrommune Therapeutics, and IgGenix. Dr Chan reports receiving grant from NIAID and NIH. Prof Leung reports receiving grants from Genentech, Incyte Corporation, and Sanofi-Genzyme; nonfinancial support from Aslan Pharmaceuticals; and personal fees from Leo Pharmaceuticals. Dr Marshall reports receiving research grant support from NIH. Prof Nadeau reports receiving grants from NIAID; National Heart, Lung, and Blood Institute (NHLBI); National Institute of Environmental Health Sciences (NIEHS); and FARE; receiving stock options from IgGenix, Seed Health, ClostraBio, Cour, and Alladapt; serving as an advisor at Cour Pharma; serving as a consultant for Excellergy, Red tree ventures, Before Brands, Alladapt, Cour, Latitude, Regeneron, and IgGenix; serving as a co-founder of Before Brands, Alladapt, Latitude, and IgGenix; serving as National Scientific Committee member at Immune Tolerance Network (ITN) and NIH clinical research centers; and having patents including, “Mixed allergen composition and methods for using the same,” “Granulocyte-based methods for detecting and monitoring immune system disorders,” and “Methods and Assays for Detecting and Quantifying Pure Subpopulations of White Blood Cells in Immune System Disorders.” Dr Radulovic reports receiving grant from NIAID and NIH. Prof Lack reports receiving grant from NIAID/NIH; having personal fees and stock options from DBV Technologies; having stock options from Mission MightyMe; and serving as a scientific consultant/advisor for Novartis, Sanofi-Genzyme, Regeneron, ALK-Abello, Reckitt Mead Johnson, and Lurie Children's Hospital. Dr Sindher receives research grant support from NIH, FARE, CoFAR, DBV, AIMMUNE, and Regeneron and has served as an advisor for Genentech. Prof Brough reports receiving grant from NIAID and NIH and receiving speaker honoraria from DBV Technologies, GlaxoSmithKline, and Sanofi. The remaining authors have no conflicts of interest to report., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Air pollution is a global problem associated with various health conditions, causing elevated rates of morbidity and mortality. Major sources of air pollutants include industrial emissions, traffic-related pollutants, and household biomass combustion, in addition to indoor pollutants from chemicals and tobacco. Various types of air pollutants originate from both human activities and natural sources. These include particulate matter, pollen, greenhouse gases, and other harmful gases. Air pollution is linked to allergic diseases, including atopic dermatitis, allergic rhinitis, allergic conjunctivitis, food allergy, and bronchial asthma. These pollutants lead to epithelial barrier dysfunction, dysbiosis, and immune dysregulation. In addition, climate change and global warming may contribute to the exacerbation and the development of allergic diseases related to air pollutants. Epigenetic changes associated with air pollutants have also been connected to the onset of allergic diseases. Furthermore, these changes can be passed down through subsequent generations, causing a higher prevalence of allergic diseases in offspring. Modulation of the aryl hydrocarbon receptor could be a valuable strategy for alleviating air pollutant-induced epidermal barrier dysfunction and atopic dermatitis. A more effective approach to preventing allergic diseases triggered by air pollutants is to reduce exposure to them. Implementing public policies aimed at safeguarding individuals from air pollutant exposure may prove to be the most efficient solution. A pressing need exists for global policy initiatives that prioritize efforts to reduce the production of air pollutants., Competing Interests: Disclosures The authors have no conflicts of interest to report., (Copyright © 2023. Published by Elsevier Inc.)

Purpose of Review: As the incidence of allergic conditions has increased in recent decades, the effects of climate change have been implicated. There is also increased knowledge on the effects of other physical influences, such as scratching and Staphylococcus aureus . The skin barrier is the first line of defense to the external environment, so understanding the ways that these factors influence skin barrier dysfunction is important., Recent Findings: Although the impact on environmental exposures has been well studied in asthma and other allergic disorders, there is now more literature on the effects of temperature, air pollution, and detergents on the skin barrier. Factors that cause skin barrier dysfunction include extreme temperatures, air pollution (including greenhouse gases and particulate matter), wildfire smoke, pollen, scratching, S. aureus, and detergents., Summary: Understanding the ways that external insults affect the skin barrier is important to further understand the mechanisms in order to inform the medical community on treatment and prevention measures for atopic conditions., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Climate change is a global threat to public health and causes or worsens various diseases including atopic dermatitis (AD), allergic, infectious, cardiovascular diseases, physical injuries, and mental disorders. The incidence of allergy, such as AD, has increased over the past several decades, and environmental factors such as climate change have been implicated as a potential mechanism. A substantial amount of literature has been published on the impact of climate factors, including cold and hot temperatures, on the skin barrier and AD. Studies in several countries have found a greater incidence of AD in children born in the colder seasons of fall and winter. The effect of cold and warm temperatures on itch, skin flares, increased outpatient visits, skin barrier dysfunction, development of AD, and asthma exacerbations have been reported. Understanding mechanisms by which changes in temperature influence allergies is critical to the development of measures for the prevention and treatment of allergic disorders, such as AD and asthma. Low and high temperatures induce the production of proinflammatory cytokines and lipid mediators such as interleukin-1β, thymic stromal lymphopoietin, and prostaglandin E2, and cause itch and flares by activation of TRPVs such as TRPV1, TRPV3, and TRPV4. TRPV antagonists may attenuate temperature-mediated itch, skin barrier dysfunction, and exacerbation of AD., (Copyright © 2023 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Atopic dermatitis (AD) and food allergy (FA) are strongly associated, with one-third of children with AD developing concomitant FA. Epithelial barrier dysfunction is important in both conditions. Genetic factors, such as filaggrin mutations and IL-4 receptor alpha chain polymorphisms, are linked to increased risk. In addition, several environmental exposures lead to reduced filaggrin and contribute to skin barrier dysfunction. Staphylococcus aureus colonization appears to contribute to AD and FA, as well as activating the type 2 immune response. Comprehensive multiomic studies using skin tape stripping have identified distinct atopic endotypes with unique characteristics of the stratum corneum lipids, proteins, S aureus abundance, and type 2 cytokine expression. Our new understanding of AD and FA presents an area of opportunity to move toward improved diagnosis and prevention of atopy., (Copyright © 2022 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)