Atopic dermatitis (AD) is an inflammatory, chronic, pruritic skin disease with a large scale of severity and a high rate of recurrence and infections due to scarring, which can seriously affect health-related quality of life.
AD-related symptoms are itching, redness, dry and scaly skin, and recurrent eczematous lesions. AD incidence has increased worldwide over the past several decades and affects 60% of the population, especially children (60% in the first year and 85% before five years old); it typically clears during adolescence but may persist into adulthood. The higher incidence in children derives from several factors such as the type of delivery, familiarity, Western diet with a high glycemic load, and pollution. AD development is characterized by external stimuli (allergens), immune mechanisms (inflammatory cytokines), and alteration of gut and skin microbial community.
The gut microbiome can strongly influence the host immune system, providing protection against pathogens and triggering an immune protective response. A dysbiotic status can increase the possibility to develop an autoimmune and inflammatory response even in a distant body area such as the skin. This correlation was described for the first time in 1930 with a theory addressing the inter-relationship between emotional states, intestinal microbiota, and systemic skin inflammation: the well-known “gut-skin-brain axis”.