Dear Colleagues,

The skin surface constitutes a complex ecosystem that supports different ecological niches. Its particular inhospitable environment, with an acidic pH and variable humidity conditions, among other characteristics, could make it difficult for microorganisms to proliferate. However, the skin microbiota, with an amazing capacity for adaptation, has evolved to become an important ally for human survival through a complex natural selection of resident microorganisms that prevent the colonization of other pathogens while working as a team with the immune system. In turn, the biotopes that harbor these microorganisms are as varied as the topography of the skin itself, and it is considered that nine out of ten human cells present symbiotic relationships with the microbiota. In human skin, we can find corineiform bacteria, staphylococci, and a smaller group made up of micrococci and Acinetobacter. Other species isolated from the skin include S. hominis, S. capitis, S. cohnii, S. haemolyticus, S. saprophyticus, S. wameri, S. xilosus, and S. simulans. Fungi such as Candida, Malassezia, Trichosporon, and Rhodotorula and mites such as Demodex folliculorum and Demodex brevis have also been isolated.

The advances in molecular techniques have been crucial for the current (even though still limited) understanding of the structure of the skin microbiota. Further investigation is needed, and research should focus on the defined aspects of the immune system–microbiota, in order to provide answers about why and what alterations in the skin ecosystem translate into diseases or a propensity for them and develop therapeutic modalities to ameliorate dysbiosis and counteract pathogens.

 In this Special Issue, we expect to gather several studies with a focus on skin microbiota in health; topography and variation by skin site; interpersonal variation; host factors; environmental factors; ecology and genomics; molecular analysis; common skin bacteria, fungi, and mites; skin disorders with a correlation to microbiota; impact of skin care products; and therapeutic opportunities. We look forward to your contribution.

Prof. Dr. Carmen Rodríguez-Cerdeira
Prof. Dr. Jacek C. Szepietowski
Prof. Gabriella Fabbrocini
Dr. Erick Martinez-Herrera
Guest Editors

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• skin flora
• microbiota
• ecosystem
• microbiology
• resident microbiota
• transient microbiota
• staphylococci and micrococci
• cutaneous microbiota and host immunity
• parasitic microbiota
• fungal microbiota
• skin microbiota variability
• variations according to sex and age
• pathological modifications
• relationship of the microbiota with some dermatoses