The Skin Microbiota: Enlisting Bacteria to Treat Dermatologic Disorders

 In Dermatology

Trevor Cates, ND

Vis Medicatrix Naturae

Research continues to reveal the benefits of a healthy microbiota of the gut and also skin.1 Many of the microbiome studies to date have focused on describing the gut microbiota, but the skin microbiota has been gaining more attention over the past 10 years.

The increase in attention is likely due to the growing number of people with chronic skin conditions. Acne is the most common skin condition in the United States, affecting close to 50 million Americans, and is the eighth most prevalent disease worldwide. In addition, 32 million people are estimated to have eczema,3 and rosacea affects over 16 million Americans.4 The changes associated with aging skin are also a top concern among the large number of baby boomers in their 50’s and beyond. These are just a few of the many dermatologic conditions that impact our patients.

The Importance of Skin Microorganisms

The growing research on the skin microbiota has revealed that the skin is colonized with a larger number of microorganisms than previously thought. Human skin is estimated to be inhabited by approximately 1 million bacteria per square centimeter.1 The microbial composition varies in different areas of the body with remarkable variability across individuals. Lifestyle, environment, hygiene, and diet, as well as age and sex, impact the makeup of the skin microbiota.

Research is also revealing more about the gut-brain-skin axis. The gut-brain-skin axis theory connects disturbances in emotional states (stress, anxiety, and depression) with changes in the gut mibrobiota as well as hyper-permeability of the gut. These gut changes create an inflammatory response that can trigger a number of dermatologic issues, including acne, eczema, and rosacea. For example, one study showed that patients with rosacea had a 10-fold greater incidence of small intestinal bacterial overgrowth (SIBO) than healthy controls,5 and another study found significantly higher rates of Helicobacter pylori infection in rosacea patients than controls.6 Acne severity has also been linked to changes in gut microbes.7

Probiotics for the Skin

Taking oral probiotics and eating prebiotic- and probiotic-rich foods appears to help address gut flora imbalances and restore healthy skin. Probiotics also have the potential for a direct effect when applied topically by supporting the skin’s natural defense barriers as well as enhancing the activity and growth of healthy skin microbiota. A well-balanced skin microbiota protects against pathogens, promotes the natural lipid barrier, and strengthens the skin immune system. Ultimately, this function helps prevent acne, eczema, and other skin disorders, as well as premature wrinkles.8-10

Topically used probiotics appear to adhere to human keratin and prevent biofilm formation.11 Research shows that topical products containing prebiotics and/or probiotics may help skin by modulating the immune system and may provide therapeutic benefits for atopic diseases.12 They also appear to improve healing of burns and scars, and improve skin rejuvenation.13

Certain topical probiotic formulations have the potential to prevent skin dysbiosis, stimulate the activity and growth of beneficial microbiota, and improve skin barrier function.12 This is particularly important for dermatologic conditions with dry, sensitive, and reactive skin. It is also something to consider after individuals are exposed to invasive cosmetic procedures or overzealous hygienic routines, as well as after using medications such as antibiotics and corticosteroids.

Various studies have shown that certain strains of topical probiotics have potential as agents for treating skin problems such as accelerated aging, acne, and atopic dermatitis; however, there is more to be learned about the specific probiotic strains and where they are best applied for each dermatologic condition.

The Acidic Nature of Skin

One of the big factors that impacts the skin microbiota is the external pH of the skin. The surface of human skin has a natural pH of about 4.5.14 This mild acidity helps to keep the skin’s microbiota in balance; a more alkaline pH (around 8 to 9) can disrupt that balance. Even water’s pH of 7 is too high for skin. After rinsing with water, rebalancing the pH to a mildly acidic level is important, especially for individuals with existing dermatologic conditions. Many common skincare products, including cleansers, moisturizers, and over-the-counter topical medications have a pH of 5.5 and higher, which can dry out skin and make it more prone to infections, eruptions, and premature aging.15

A skincare product’s formula determines its pH. There are many natural ingredients, such as citric acid, that reduce the pH to the mildly acidic range. Not all skin care products are made with mild acidity in mind. You also don’t want skincare products to be too acidic (below 4.5). If the pH is not listed, you can contact the manufacturer and ask for it.

Certain oils can also help to support mild acidity and have other balancing effects for skin. For example, argan kernel oil is thought to restore resilience to the acid mantle, impart luminosity, and protect against dryness. Argan oil is rich in vitamin E, fatty acids, beta-carotene and carotenoids, and phytosterols. Argan oil appears to be a good option for a variety of skin types, including acne-prone skin.

Clinical Wisdom

In my practice, I find that a combination approach to addressing the skin microbiota is most effective at supporting healthy, radiant skin. For my patients, I recommend addressing gut dysbiosis with a diet that is high in fiber and includes probiotic-rich foods such as fermented vegetables. In addition, I perform specialty lab testing to determine specific gut and skin dysbiosis issues and target treatment accordingly. Topically, I recommend using a skincare regime that supports a pH range of 4.5-5.0 and provide recipes for patients to make their own skincare products at home, such as a blend of gluten-free oat flour and plain organic yogurt (equal parts). Additionally, compounded topical treatments addressing skin dysbiosis can sometimes provide relief, depending upon the individual’s skin condition.


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  14. Lambers H, Piessens S, Bloem A, et al. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmet Sci. 2006;28(5):359–370.
  15. Jung YC, Kim EJ, Cho JC, et al. Effect of skin pH for wrinkle formation on Asian: Korean, Vietnamese and Singaporean. J Eur Acad Dermatol Venereol. 2013;27(3):e328–e332.

Dr Trevor Cates was the first woman licensed as a naturopathic doctor in the state of California, appointed by former Governor Arnold Schwarzenegger to California’s Bureau of Naturopathic Medicine Advisory Council. She has worked with world-renowned spas and sees patients in her private practice in Park City, Utah. Her book Clean Skin from Within was released on March 15, 2017 and outlines her 2-week protocol. Dr Cates’ “The Spa Dr” skincare and supplement lines are formulated with natural and organic ingredients designed to help individuals achieve clean glowing skin.

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