key: cord-0704126-1i6zbo4g
authors: Rinaldi, Fabio; Giuliani, Giammaria; Pinto, Daniela
title: Importance of preserving the resident microflora of the skin to improve immunological response
date: 2021-05-10
journal: J Investig Med
DOI: 10.1136/jim-2021-001823
sha: e0d844f9adcc511c7884f55b3965a6d87a7760c2
doc_id: 704126
cord_uid: 1i6zbo4g

nan

As an interface with the outside environment, skin is colonized by a diverse collection of microorganisms-including bacteria, fungi, archaea, and viruses, protecting against invasion by more harmful or pathogenic organisms.

Skin acts also as an immunological barrier 1 by educating the billions of T cells inside the skin. This role is crucial in wounding and infection and for modulating the commensal microbiota that colonizes the skin. Indeed, by means of pattern recognition receptors, such as Toll-like receptors, mannose receptors, and the nucleotide-binding oligomerization domainlike receptor (NOD receptors), keratinocytes continuously sample the microbiota colonizing the skin surface. 2 In this view, skin microbiota must be considered as one of the main factors influencing the response to infection since it has been recognized as a necessary element of immunity, being able to regulate the immune response of the host and also to maintain homeostasis. 3 Hands represent a primary vector for infection transmission, including the so actual COVID-19 infection. The continuous presence of the virus forces almost all people to use Personal protective equipment (PPE) and disinfectant gels. They are fundamental, but they determine a series of skin alterations such as the disruption of the skin microbiome up to irritative dermatitis and alterations of the protective skin barrier. 4 5 Because of the alteration of the skin barrier, there is an increase in the ability of microorganisms to spread through the skin and a decrease of the skin's immune response.

Hand microbiota is, among other body sites, one of the most subjected to a temporal variability 6 because of handwashing routine and hand sanitizer usage. These routines help us to protect against pathogens but what are they doing to hand's resident skin microbiota? Handwashing minimally impacts on microbiota healthiness but the widespread use of disinfectants, especially during COVID-19, has been reported to be detrimental to hand's microbiota homeostasis and antibacterial potential. 4 This is the consequence of the reduction of species richness leading also to the alteration of skin structure (eg, barrier, hydrolipidic film) and functions such as immune response, colonization resistance (due to the presence of triclosan in hand sanitizers) but also the lowering of the production of antimicrobial peptides (dermcidin, LL-37) and exacerbation of inflammatory milieu. Indeed, the high content of alcohol in these products is responsible also for the dryness of the skin as for skin chronic inflammation. 

The coordinated response of the physical and antimicrobial peptide barriers of the skin

The skin microbiome

The microbiota, a necessary element of immunity

Consensus of Chinese experts on protection of skin and mucous membrane barrier for health-care workers fighting against coronavirus disease 2019

Skin damage among health care workers managing coronavirus disease-2019

Review of human hand microbiome research