The perfect skin microbiome for life?! Microbial changes across our lifespan
First things first, there is no “one-size-fits-all” ideal skin microbiome! Not only is each skin microbiome unique, it also doesn’t even stay the same during a person’s life. Let’s uncover the factors that determine how it changes with age and see which disruptions may impact lifelong health.
One skin microbiome?
Our skin is constantly interacting with factors that influence its microbial composition, like clothes, other people, climate, and cosmetics. While some core skin microbial taxa are the same, we all have unique genetics, skin physiology, environment and a distinct way in which microbes interact with their host and each other. 
The skin microbiome is not even the same across the whole body. Depending on physical characteristics like hair follicles, sweat glands and moisture, we see different microbial ecosystems on different body sites. 
What is a healthy skin microbiome?
One important job of the microbiota is to prevent the overgrowth of pathogenic organisms like Staphylococcus aureus. If they can maintain the integrity of the skin barrier, we can say it’s a healthy, balanced microbiome.  In many cases, microbial abundance and diversity are indicators for a healthy microbiome. A loss of community diversity, however, indicates a disrupted or dysbiotic skin microbiome. Which can lead to increased inflammation, infections, and the development of skin diseases. 
Changes in the skin microbiome as we age
The skin’s maturation process starts with birth, as it transitions from the warm, wet utero to a cool, dry environment.  The skin of newborns and infants is characterized by higher pH, water content, and antimicrobial properties. In early childhood the microbiome is shaped by our environment, including the people we are close to. A disruption of the microbial equilibrium can increase the risk for atopic dermatitis and allergies. [1, 4]
Changes in sex hormones during puberty alter the structure and function of the skin, like developing sebaceous and sweat glands . Adolescent skin is dominated by lipophilic microbes like Corynebacterium, Cutibacterium acnes, and Malassezia . Sex hormones promote wound healing and strengthen the skin’s barrier by stimulating collagen synthesis. However, puberty-driven imbalances in the microbiome can lead to skin disorders like acne vulgaris and psoriasis. 
In matured, adult skin, factors like pH, sebum production, sweat composition and resilient immunity contribute to stable microbial communities over years, despite external influences.  With advancing age, we see a reduction in cell regeneration, decreased water retention, slower immune responses, and an increased risk for infections. Potentially leading to diseases like dry skin, seborrheic dermatitis or rosacea. 
Bottom line, this microenvironment is dynamic and changes with age and our environment. Showing once again how important caretaking our microbial friends is during our entire life.
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