You can change into clean clothes every day, but your skin is that permanent physical barrier that prevents the invasion of disease-causing bacteria, fungi, and viruses.
The harsh dry physical landscape of skin, particularly the nutrient-poor, acidic environment, is hostile to disease-causing bacteria. The skin barrier is designed to be impermeable, meaning it keeps water in and bacteria and microorganisms out.
Daily life actions, such as touching, eating, and breathing, shape the human microbiome from its inception and can alter its composition throughout all life stages of an individual.
Although people have been manipulating the skin microbiome, often beneficially, by washing and using cosmetics and topical antiseptics, recent research showed that the healthy human skin microbiome is stable over time despite external exposures.