The prevalence of many chronic noncommunicable diseases has been steadily rising over the past six decades. During this time, over 350,000 new chemical substances have been introduced to the lives of humans. In recent years, the epithelial barrier theory came to light explaining the growing prevalence and exacerbations of these diseases worldwide. It attributes their onset to a functionally impaired epithelial barrier triggered by the toxicity of the exposed substances, associated with microbial dysbiosis, immune system activation, and inflammation. Diseases encompassed by the epithelial barrier theory share common features such as an increased prevalence after the 1960s or 2000s that cannot (solely) be accounted for by the emergence of improved diagnostic methods. Other common traits include epithelial barrier defects, microbial dysbiosis with loss of commensals and colonization of opportunistic pathogens, and circulating inflammatory cells and cytokines. In addition, practically unrelated diseases that fulfill these criteria have started to emerge as multimorbidities during the last decades. Here, we provide a comprehensive overview of diseases encompassed by the epithelial barrier theory and discuss evidence and similarities for their epidemiology, genetic susceptibility, epithelial barrier dysfunction, microbial dysbiosis, and tissue inflammation.

The epithelial barrier theory links the recent rise in chronic non-communicable diseases, notably autoimmune and allergic disorders, to environmental agents disrupting the epithelial barrier. Global pollution and environmental toxic agent exposure have worsened over six decades because of uncontrolled growth, modernization, and industrialization, affecting human health. Introducing new chemicals without any reasonable control of their health effects through these years has led to documented adverse effects, especially on the skin and mucosal epithelial barriers. These substances, such as particulate matter, detergents, surfactants, food emulsifiers, micro- and nano-plastics, diesel exhaust, cigarette smoke, and ozone, have been shown to compromise the epithelial barrier integrity. This disruption is linked to the opening of the tight-junction barriers, inflammation, cell death, oxidative stress, and metabolic regulation. Consideration must be given to the interplay of toxic substances, underlying inflammatory diseases, and medications, especially in affected tissues. This review article discusses the detrimental effect of environmental barrier-damaging compounds on human health and involves cellular and molecular mechanisms.

Since the 1960s, more than 350,000 new chemicals have been introduced into the lives of humans and domestic animals. Many of them have become part of modern life and some are affecting nature as pollutants. Yet, our comprehension of their potential health risks for both humans and animals remains partial. The “epithelial barrier theory” suggests that genetic predisposition and exposure to diverse factors damaging the epithelial barriers contribute to the emergence of allergic and autoimmune conditions. Impaired epithelial barriers, microbial dysbiosis, and tissue inflammation have been observed in a high number of mucosal inflammatory, autoimmune and neuropsychiatric diseases, many of which showed increased prevalence in the last decades. Pets, especially cats and dogs, share living spaces with humans and are exposed to household cleaners, personal care products, air pollutants, and microplastics. The utilisation of cosmetic products and food additives for pets is on the rise, unfortunately, accompanied by less rigorous safety regulations than those governing human products. In this review, we explore the implications of disruptions in epithelial barriers on the well‐being of companion animals, drawing comparisons with humans, and endeavour to elucidate the spectrum of diseases that afflict them. In addition, future research areas with the interconnectedness of human, animal, and environmental well‐being are highlighted in line with the “One Health” concept.

Immunoglobulin G4 (IgG4), a unique subclass of IgG antibodies, plays diverse roles in human health and disease. Its distinct features, such as Fab-arm exchange and specific mutations, confer reduced effector functions compared to other IgG subclasses. In health, IgG4 responses contribute to immune tolerance, particularly in the context of allergen-specific immunotherapy (AIT), where they can mediate tolerance to environmental antigens, inhibit IgE-dependent mast cell degranulation, and compete with IgE for allergen binding. This helps in attenuating allergic symptoms and is associated with increased levels of allergen-specific IgG4. However, in disease scenarios, the role of IgG4 is complex. IgG4 lacks complement fixation and, thus, shows a reduced ability to activate immune effector pathways, it was initially thought to be protective against autoimmune diseases. However, emerging evidence suggests that it can contribute to pathology. For instance, IgG4 autoantibodies against specific antigens can aggravate conditions in certain autoimmune disorders. In some cancers, it may play a role in immune evasion, with higher levels correlating with poor patient survival, albeit in others, its exact function remains elusive. Overall, understanding the precise role of IgG4 in various physiological and pathological conditions is crucial for developing targeted therapeutic strategies and improving patient outcomes.

The present study focused on evaluating the effects of beef marination on quality traits and consumer acceptability. In this context, m. longissimus thoracis et lumborum and m. semimembranosus samples (n = 192) were obtained from Aberdeen Angus, Hereford, Charolais, and Limousine bulls and were marinated with milk (pasteurized, 100%), garlic and olive oil (2.35 g/500 mL), and lemon (citrus) juice (31% orange juice, 31% lemon juice, 38% distilled water) for 12, 24, and 72 h. Marinade components were selected based on traditional culinary practices and their scientifically proven effects on meat quality. Beef samples on day 0 and non-marinated samples were used as control groups. Beef color, water holding capacity, pH, cooking loss, and Warner–Bratzler shear force were measured three times for each sample. A taste panel assessment was performed to determine the sensory characteristics. Statistical analysis was performed using general linear model (GLM) procedures followed by Tukey’s post-hoc comparison. Results revealed that marination time, as well as its two- and three-way interactions, significantly influenced beef quality parameters. These results indicate that the cattle breed is an important factor in evaluating the effectiveness of beef marination applications. The olive oil−garlic marinade was the most preferred by the panel across both types of muscle, as indicated by sensory evaluation results. The findings will not only enrich the scientific literature but also have practical implications for the beef industry.