One Health in allergology: A concept that connects humans, animals, plants, and the environment

One Health is “a collaborative effort of multiple disciplines – working locally, nationally, and globally – to attain optimal health for people, animals, and the environment ”, the so-called One Health triad1 (Figure 1). Historically, aspects of One Health were already discussed in the fourth century by Hippocrates, who realized that a clean environment is very important for human health.1 More recently, Rudolf Virchow (1821–1902) coined the term “zoonosis” in 1880 and fathered modern One Health in the sense of One Medicine by strongly supporting the view of human and animal health being linked to each other.1 Amuasi et al2 even propose that the One Health policy is vital to ensure health of and on the planet, and avoid future catastrophes: “One Health, which recognizes the fundamental interconnectedness of humans, animals, and their shared environment, is key to ensuring the healthy and sustainable future of the planet.” Prestigiously, WHO has also taken up the One Health idea, concentrating on food safety, combatting antibiotic resistance, and controlling zoonoses, all for achieving better public health outcomes.3 One Health thus is a timely concept in terms of the current COVID-19 pandemic, considering the interspecies viral transmission (Pali-Schöll et al, EAACI Position Paper in revision). The importance of the One Health concept has also been acknowledged by the opinion leaders of the European Academy of Allergy and Clinical Immunology (EAACI), who joined into the One Health Summit Strategic Advisory Group of the Global Risk Forum Davos in 2015 to prepare the implementation of this concept into the EAACI profile. With a strong foundation in the Working Group (WG) for Comparative and Veterinary Allergology, this focus led to the foundation of an independent EAACI WG dedicated to One Health in 2021.4 A One Health approach is needed in allergolgy, as allergic diseases are found in human and non-human mammals alike,5-7, the prevalence of some of them still on the rise, and the diagnosis and treatment comparable in many cases.8, 9 For all mammalian species affected by allergies, a plethora of common factors seems to be responsible for disease development, duration, and severity (Figure 1). Effects of the global warming, climate change, and air pollution have already become clear,10 among them, we find novel species of plants (eg, ragweed) and animals (eg, insects like Polistes spp.) in geographical regions where they have not been resident before. The early and prolonged blooming season due to increased temperature leads to higher and prolonged allergen exposure for patients, and allergenicity of molecules becomes more potent in combination with CO2,11 ozone,12 or pollution contributing fine- and ultra-fine particles.13 Other factors studied individually, but less investigated in their interconnectedness within the One Health triad, are the environmental hygiene status (ie, meeting microbes, parasites, and dirty soil); body hygiene (shampoos, shaving, deodorants, perfumes, disinfectants, etc.); diet and food composition (dietary fiber, micronutrients); nutritional status (nutrient deficiencies); food processing (cooking, pasteurization, frying, etc.); microbiota (endogenous on skin and in gut; and exogenous on plants andin soil); pollution of water, air, and environment (eg, diesel-exhaust particles); medications like antibiotics or acid-suppressing drugs contributing to increased allergenicity of encountered proteins14, 15; and many more. All of these factors may have a varying influence on development and outcome of allergic diseases. Therefore, to successfully combine them, a well-coordinated approach in humans and in animals is necessary. How the One Health approach can be applied to allergy, is discussed here by lipocalins in cow's milk as example. Cow's milk can be allergenic, while raw milk protects against allergies.16 The major whey protein beta-lactoglobulin (BLG), a lipocalin, is a typical milk allergen (Bos d 5), but can also mediate immune resilience. Proteins of the lipocalin family are carrier molecules, for example, for iron-siderophore complexes, vitamins A and D, and zinc. It was shown that the loading of BLG with vitamins and iron complexes is decisive: When BLG shuttles ligands into immune cells, it causes immune-resilience, while uptake without ligands evokes a Th2-response in vitro, resulting in allergy in murine models.17-22 Moreover, symptom reduction could be achieved by consumption of loaded BLG in house dust-mite allergic23 and birch pollen allergic patients.24 Apart from this being an important immunological observation, following the One Health concept, we must scrutinize its systematic impact for humans and animals. The following questions emerge: Which factors during milk processing have an impact on the essential cargo and hence allergenicity? Does the feed of the cow relate to the loading of the protein? Can stress, disease, living/growing conditions, nutritional state of the animals or environmental conditions affect ligand availability and binding efficacy to BLG? How can we strategically communicate important findings to industry, politicians, vets, and breeders to improve husbandry conditions, food production procedures and thereby prevent allergies? Many more One Health aspects and questions in the context of allergic diseases are still un-addressed: In line with the WHO definition of One Health,3 to address these and upcoming questions in allergology, interdisciplinarity from a broad range of fields of expertise is required, including allergology and immunology, internal medicine, ENT, pediatrics, dermatology, nutrition/dietetics, ecology, biology, agriculture, veterinary medicine, aerobiology, microplastics, water ecology, and many more. An interdisciplinary and holistic approach is required to prevent diseases like the allergy epidemic, natural catastrophes, and devastation of the planet Earth. This will only be possible by communicating, discussing, and acting according to the One Health concept in an interdisciplinary strategic attempt, including public and lay people, politicians and legislative, practitioners and scientists. One Health has thus not only become a strategic program in the WHO, but also recently a thematic program in EAACI. Dr. Jensen-Jarolim and Dr. Roth-Walter are inventors of EP2894478; “LCN2 as a tool for allergy diagnostic and therapy,” EP 14150965.3, Year: 01/2014; US 14/204,570, owned by Biomedical International R + D GmbH, Vienna, Austria. Dr. Jensen-Jarolim is shareholder in this company. Dr. Pali-Schöll has nothing to disclose.