Exogenous factors in the pathogenesis of atopic dermatitis: Irritants and cutaneous infections

Abstract

Atopic dermatitis (AD) is a chronic relapsing inflammatory cutaneous disease that is often associated with other atopic symptoms, such as food allergy, allergic rhinitis and asthma, leading to significant morbidity and healthcare costs. The pathogenesis of AD is complicated and multifactorial. Although the aetiology of AD remains incompletely understood, recent studies have provided further insight into AD pathophysiology, demonstrating that the interaction among genetic predisposition, immune dysfunction and environmental provocation factors contributes to its development. However, the increasing prevalence of AD suggests that environmental factors such as irritation and cutaneous infection play a crucial role in triggering and/or aggravating the disease. Of note, AD skin is susceptible to bacterial, fungal and viral infections, and microorganisms may colonize the skin and aggravate AD symptoms. Overall, understanding the mechanisms by which these risk factors affect the cutaneous immunity of patients with AD is of great importance for developing a precision medicine approach for treatment. This review summarizes recent developments in exogenous factors involved in the pathogenesis of AD, with special emphasis on irritants and microbial infections.

Serum 25-Hydroxyvitamin D Concentrations and Atopic Dermatitis in Early Childhood: Findings from the Japan Environment and Children’s Study

“…Studies also revealed that VitD promotes human cathelicidin generation, which has been considered insufficient in AD [ 10 , 13 ] and improves innate immunity. Given that the mechanism of development of AD relates to skin barrier dysfunction and immune response dysregulation [ 14 , 15 ], VitD might be related thereto. Epidemiological studies have also shown evidence with regard to VitD and the development of atopic eczema [ 16 ].…”

Genetic Variants in Epidermal Differentiation Complex Genes as Predictive Biomarkers for Atopic Eczema, Allergic Sensitization, and Eczema-Associated Asthma in a 6-Year Follow-Up Case–Control Study in Children

“…Other risk factors supported by strong epidemiological data are: living in an urban area associated with specific hygiene-related exposures, increased stress, and higher exposure to traffic-related air pollution, including particulate matter, sulfur, carbon, nitrogen, and benzene components connected with urbanization and industrialization [ 90 , 91 , 92 ]. Specific external irritants, such as alkaline soaps, detergents microplastics, nanoparticles, and hard water have also been reported to play important roles in the development and aggravation of atopic eczema [ 93 , 94 ]. There is some evidence for the effects of maternal or postnatal tobacco exposure, long-term exclusive breastfeeding, routine childhood vaccinations, viral or bacterial infections, and farm environments; however, epidemiological data are still inconsistent [ 89 , 90 , 91 , 95 ].…”

Role of club cell 16‐kDa secretory protein in asthmatic airways

“…Der p1 plays as a major allergen and has a proteinase activity (as an irritant) on AECs (inducing intracellular oxidative stress and impairing epithelial barrier). 16,24 The release of CC16 from Clara cells was increased after acute exposure to environmental factors (smoke and allergens) but decreased in chronic exposure condition with progressive damage of AECs. [25][26][27] The present study assessed CC16 production from AECs in response to Der p1 in a time-dependent manner.…”