## 1 Introduction  
The human body is colonized by trillions of microorganisms, including distinct species of bacteria, fungi, viruses, and protozoa. Collectively, these microorganisms and their genetic makeup form a constantly changing microbial community that resides in various regions of the body and significantly influences the well-being, illness, maturation, and progression of their host, being commonly known as the human microbiome [1].  
The microbiome is the genetic heritage of microorganisms that live with humans, classified as the community of microscopic organisms that colonize various areas of the human body, whether superficial or deep, such as the genitourinary system, respiratory system, and gastrointestinal system, among others. Its development is a dynamic process that varies throughout life, coexisting with its host and actively participating in many biological processes in the human body [1]. This involvement of the microbiome in various functions makes it essential for maintaining homeostatic balance, and its impairment can lead to problems for the host, such as the emergence of several diseases, including cardiovascular diseases [2]; autoimmune diseases, namely in rheumatoid arthritis, Type 1 diabetes, atopic asthma, and atopic dermatitis [3]; and colon cancer [4].  
Contrary to the human genome, which is rarely influenced by external factors, the human microbiome is characterized by some volatility, as demonstrated by the use of antibiotics, changes in diet, or states of infection in the host organism, which can subsequently lead to significant modifications in host microorganisms. Lifestyle and exercise also have a powerful impact on the composition of the human microbiome [5; 6; 7]. Therefore, several factors shape the microbiome, preventing the development and prevalence of various diseases and leading to a healthier life. Among these factors, the Mediterranean diet, medicinal therapies, the use of probiotics and prebiotics, and even fecal bacterial transplantation stand out [8].  
The human body site that harbors the largest number and diversity of microorganisms is the gastrointestinal tract, specifically the intestine, which exerts a greater influence on human homeostatic mechanisms [9]. Several diseases and their risk factors have been identified as examples of the interaction between the host and the gut microbiome [10; 11]. With the development of culture-independent methods, it has become possible to better identify microorganisms and their genomes. These microorganisms can have either harmful or beneficial effects on their host. Concerning skin microbiota, _Staphylococci_ species are considered harmful, _Cutibacterium_ often being cited as beneficial [12]. Concerning gut microbiota, the presence of _Lactobacillus_ and _Bifidobacterium_ species is usually considered beneficial [13]. There are indications that microorganisms, both on the skin and in the gut, might impact the progression of atopic dermatitis. While antiseptic treatments have been in use for many years, recent advancements in traditional-culture-based techniques and cutting-edge metagenomics are shedding light on the potential of targeted dysbiosis treatment as a potential component of an integrated therapeutic approach in the future [14; 15; 16].  
Therefore, this manuscript aimed to provide an updated overview of the intriguing relationship between the human microbiome and diseases, seeking to establish the importance of the microbiome in health and disease, focusing on the case of atopic dermatitis. For this purpose, a literature search was conducted using the keywords human microbiome, skin diseases, atopic dermatitis, probiotics, and prebiotics, in a scientific database, selecting the most-relevant scientific articles for this work concerning the purpose of the manuscript.