There are billions of microbes living on your skin, and believe it or not, they belong there! This layer of microorganisms is called the microbiome. Bacteria, fungi, viruses, and even mites make up this diverse community of flora that helps to protect you and ensure optimal skin health.

About Your Microbiome

The microbiome contains thousands of different species of microbes, including both good and bad bacteria found on human skin. The best way to envision these microscopic communities is to picture different neighborhoods of skin housing different types of bacteria, yeast, and viruses. Those that thrive in oily environments are different than those that live in moist or hair-bearing areas. The different factors that determine the community of flora include:

  • Body temperature
  • Skin thickness
  • Skin pH (acidity)
  • Density of hair follicles and oil glands
  • Size of skin folds

The microorganisms work together as a unit to maintain conditions that optimize skin function. People spend so much time trying to rid themselves of germs that it's easy to forget that not all bacteria are bad. Science has shown that skin flora does not usually cause disease and is either commensal, meaning not harmful, or mutualistic, offering an overall benefit.

The Good Guys

The bacterial species Staphylococcus, Propionibacterium, Streptococcus, and Corynebacterium are associated with skin health. These bacteria guide how your skin appears and acts. More specifically, a well-functioning microbiome can provide protection against skin infection by preventing the overgrowth of other "bad" bacteria, protect against external and environmental factors, keep inflammation in check, promote wound healing, and create a barrier to some allergens and environmental toxins.

In examining one of these groups further, studies have shown a correlation of low bacteria with skin disease. For example, patients with chronic skin diseases, such as psoriasis and atopic dermatitis, seemingly have reduced populations of Propionibacterium. This is just one of many examples illustrating the symbiotic relationship between these organisms and the health of your skin barrier.


Just as an out-of-sync sports team or office with an uncooperative co-worker can't deliver its best results, an off-balance microbiome leads to poor performance—and in this case, skin pathology. Dysbiosis, the scientific term for this imbalance, occurs when harmful strains of bacteria such as Staphylococcus aureus or Pseudomonas settle in and wreak havoc. Dysbiosis can lead to skin infection, irritation, inflammation, or disease. Interestingly, certain bacterial species can have different strains, some of which benefit the biome while others harm it.

Microbiome Disrupters

Disruption of your skin's protective barrier may be followed by dysbiosis. Rubbing, scrubbing, shaving, waxing, and plucking are just some of the ways that beauty routines can contribute to skin barrier irritation. Harsh products, such as alcohol-based toners, abrasive mechanical exfoliators, and soap-based cleansers, can strip the stratum corneum (the skin's outermost layer), creating disarray within the environment where good, mutualistic bacteria live. Even minor trauma or shifts in pH can knock your microflora out of balance.

The moral of the story: gentle skin care is required to maintain the integrity of the delicate microbiome. In order to do this, it is very important that your daily products don't strip the barrier and that they respect the skin's natural pH.

Putting It All Together

Especially during cold and flu season, when avoiding germs is top of mind, it is important to remember that some bacteria actually serve a very important role in skin health. After all, the skin is an often overlooked but important part of the immune system. When it comes to bacteria found on human skin, any imbalance in your innate microbiome can affect the overall appearance and integrity of your largest organ. Being mindful of the skin care routines and products you use on a daily basis can help to maintain a robust, well-functioning biome.


  • Mona Gohara, MD

    Dr. Mona Gohara is a Connecticut-based Dermatologist and associate professor of Dermatology at Yale School of Medicine. She has a particular interest in skin cancer prevention and treatment for skin of color. Dr. Gohara spends a lot of time outdoors with her husband, son, and two dogs, Coco and Cleo. They all wear sunscreen.

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