The skin is a living, dynamic ecosystem, and a barrier to the environment

The skin is our largest organ and serves as a living barrier between our body and the environment. It helps regulate body temperature and interacts with the immune system. Beyond these functions, the skin is home to a dynamic and diverse ecosystem of microbes. The surface of the skin has a slightly acidic pH (around 5.0—so it’s important to check your skincare products’ pH), which helps maintain the balance of these microbes1.

Factors like age, diet, hygiene, and clothing may impact the skin microbiome. Frequent washing with harsh soaps can disrupt the skin’s natural microbiome, stripping away beneficial oils and microbes. Maintaining a healthy skin microbiome, combined with proper care and attention to diet and hygiene, is important for promoting overall skin health and preventing common skin problems.

 

How does the skin microbiome compare to the gut microbiome?

The skin is colonized by a diverse community of microorganisms — including bacteria, fungi and viruses — as well as mites that evolve throughout life. Most bacteria on the skin are aerobic, meaning they thrive in oxygen-rich environments—unlike the ones from gut microbiome. The distribution of these microbes varies depending on the body part (hand vs. armpit) that differs of skin type whether it’s oily, dry, or moist. Like the gut microbiota, the skin’s microbial colonization begins at birth and is influenced by factors such as the mother’s diet during pregnancy, delivery method (vaginal or C-section), skin contact with others, breastfeeding, antibiotic use (before and after birth), and environmental exposure 2.

As we age, the composition of the skin’s microbiota changes. During puberty, for instance, bacteria associated with oily skin increase. In adulthood, the skin’s microbial community stabilizes, even though it continues to be influenced by environmental factors 2. Dr. Caroline Le Poole, an immunologist and dermatologist working at Northwestern University Chicago, USA, commented: “It seems that the skin can sustain itself without relying heavily on support from the entire body. Unlike the gut, the skin is more autonomous.”

 

What language do the gut and the skin speak?

“The full communication between the skin and the gut is still not fully understood. We have pieces of information with the short chain fatty acids (SCFAs; beneficial molecule produced by the bacteria) and the immune system, but we are still missing the big picture,” explained Dr. Le Poole, whose research focuses on exploring opposite ends of the immune system spectrum—from autoimmune diseases like vitiligo to cancer, such as melanoma.

The skin and gut microbiomes communicate through the gut-skin axis, where changes in one can influence the health of the other. “We noticed that oral antibiotics had a greater impact on skin diseases than topical antibiotics,” noted Dr. Le Poole.

The gut microbiome influences skin health by producing substances like SCFAs, which help regulate inflammation. When the gut microbiome becomes unbalanced (a condition known as dysbiosis), it can lead to chronic inflammation that may manifest as skin issues such as acne, eczema, or psoriasis3. Food allergies are another example of this gut-skin link—when certain foods cause an allergic reaction in the gut, the skin can break out in rashes, however the connection between the two is still unclear 4.

Conversely, the skin microbiome can also influence gut health. As Dr. Le Poole explains, “Once the integrity of the skin is compromised, pathogens can easily breach the barrier and trigger inflammation, disrupting the delicate symbiosis and sending signals over greater distances to the gut”. Severe burns can compromise the skin’s barrier, potentially leading to bacterial infections and gut dysfunction5. Vitamin D, primarily synthesized in the skin through sunlight exposure, plays a key role in maintaining the gut’s barrier integrity and supporting a healthy microbiome. It also helps reduce skin inflammation. Research conducted on COVID-19 pandemic6 as well as long-COVID (with altered gut microbiota composition)7 showed that people with adequate Vitamin D levels had better immune responses and less severe symptoms.

 

How to keep your skin healthy:

Hygiene and Hydration

“Keep your skin hydrated, but don’t overdo it, as clogging the pores can be counterproductive,” advises the expert. “The skin self-regulates naturally, and using too many products can disrupt its natural balance.” Skincare products with a high pH can irritate the skin, cause dehydration, and disrupt the skin’s natural microbiota. Stress can affect both your skin and gut, so practicing relaxation techniques might help.

Healthy Diet

What you eat often shows up on your skin! A diet high in sugar and dairy can lead to acne, while one rich in fruits, vegetables, legumes, and nuts—such as the Mediterranean diet—supports a healthy gut, reduces inflammation, and can improve skin health.

Pre, Pro, and Postbiotics

Some skincare products now include prebiotics, probiotics, and postbiotics to help balance the skin’s natural microbiome11. While these products show promise, this area of research is still in its early stages, and more studies are needed to understand how they truly impact skin health. There is also increasing interest in oral probiotics for balancing the gut microbiome, reducing inflammation, and improving skin conditions12. Dr. Le Poole noted, “Most of the focus has been on the skin microbiome, especially when skin integrity is compromised, as in atopic dermatitis or psoriasis. It is surprising that the gut microbiome has not received as much attention, given its potential role“.

Sunscreen

“Once again, the key word is balance. If you don’t get enough sun exposure, you might miss out on the beneficial effects of vitamin D synthesis on the immune system. However, overexposure can lead to genotoxicity (gene mutations) and a higher risk of cancer, especially if your natural sun protection is low,” warned Dr. Le Poole. Using sunscreen is essential to protect your skin from UV damage. You should also adopt healthy sun habits, such as avoiding exposure between 11 a.m. and 3 p.m., and refraining from prolonged sunbathing without protection, as it can increase the risk of skin cancer. Some studies in mice and human suggest that certain probiotics might even help protect skin cells from UV damage by improving hydration and boosting antioxidant activity10. Melanin, the skin’s natural pigment with antioxidant properties, helps protect against UV damage, and may also preserve the skin’s microbial balance by reducing environmental stress.

 

Conclusion

The gut-skin axis shows a strong connection between gut health and skin conditions. Current studies are developing microbiome-targeted therapies using probiotics, prebiotics, and postbiotics to benefit both skin and gut health and show promise in managing skin conditions such as psoriasis, eczema, and acne.

 

Spotlight on some skin conditions:

Aging-Related

Changes in the skin microbiome and oxidative stress influence skin aging. Like us, cells can experience stress, and when they do, they do not function properly. While they do not need meditation, antioxidant substances can help protect them. One molecule primarily produced in the gut, called GABA, plays a role in maintaining skin elasticity by supporting collagen production 3.

Bacterial-Related

  • Acne, which affects 85-90% of people aged 12-24, causes pimples, blackheads, and occasionally painful cysts. Acne is caused by clogged pores and the presence of the bacteria named Cutibacterium acnes. Diets high in fat and sugar may worsen acne by increasing sebum production and by creating an environment conducive to the growth of the pathogens 3.
  • Eczema (atopic dermatitis) leads to itchy, inflamed patches of skin and can be triggered by food or environmental allergens. Eczema is associated with an overgrowth of Staphylococcus aureus and an imbalance in the skin microbiome.

Autoimmune Disease

  • Psoriasis is a chronic autoimmune disease where the immune system attacks healthy skin cells, causing red, scaly patches 3. Psoriasis is linked to imbalances in the gut and skin microbiome, and people with psoriasis are at a higher risk of developing gut diseases like inflammatory bowel disease (IBD) or celiac disease.
  • Lupus, a systemic autoimmune disease, affects the skin, causing rashes and inflammation. People with lupus tend to have distinct gut microbiomes compared to healthy individuals 8.
  • Vitiligo is an autoimmune disease characterized by patches of white skin due to the loss of melanocytes, the cells responsible for producing melanin (skin pigment) 9. People with vitiligo exhibit distinct gut and skin microbiomes. “While the foundation of vitiligo is genetic, our research has shown that individuals with active vitiligo have a distinct gut microbiome compared to those with inactive disease,” explained Dr. Le Poole. “We also observed that certain nutrients were lacking in the diets of people with active vitiligo, suggesting that dietary interventions might help manage symptoms and influence the state of the disease.”

Cancer-Related

The most common types of skin cancer include melanoma, basal cell carcinoma, and squamous cell carcinoma, which are largely caused by UV damage and genetic factors. Emerging research suggests that imbalances in the skin microbiome may also contribute to the development of skin cancer development 10.

 

References:

  1. Sarah G. Brooks, Rami H. Mahmoud, Rachel R. Lin, Joachim W. Fluhr, Gil Yosipovitch. The Skin Acid Mantle: An Update on Skin pH. J Invest Dermatol. 2024, ISSN 0022-202X.
  2. Shivani Sinha, Gloria Lin, Katalin Ferenczi. The skin microbiome and the gut-skin axis. Clinics in Dermatology. 2021, 39:(5)829-839.
  3. Carmona-Cruz S, Orozco-Covarrubias L, Sáez-de-Ocariz M. The Human Skin Microbiome in Selected Cutaneous Diseases. Front Cell Infect Microbiol. 2022 Mar 7;12:834135.
  4. van Splunter M, Liu L, van Neerven RJJ, Wichers HJ, Hettinga KA, de Jong NW. Mechanisms Underlying the Skin-Gut Cross Talk in the Development of IgE-Mediated Food Allergy. Nutrients. 2020 Dec 15;12(12):3830.
  5. Corcione S, Lupia T, De Rosa FG; Host and Microbiota Interaction Study Group (ESGHAMI) of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). Microbiome in the setting of burn patients: implications for infections and clinical outcomes. Burns Trauma. 2020 Aug 14;8:tkaa033.
  6. Sharun, Khan; Tiwari, Ruchi; Dhama, Kuldeep. COVID-19 and sunlight: Impact on SARS-CoV-2 transmissibility, morbidity, and mortality. Annals of Medicine & Surgery 66, June 2021.
  7. Davis, H.E., McCorkell, L., Vogel, J.M. et al. Long COVID: major findings, mechanisms and recommendations. Nat Rev Microbiol 21, 133–146 (2023).
  8. Wang Y, Wu H, Yan C, Huang R, Li K, Du Y, Jin X, Zhu G, Zeng H, Li B. Alterations of the microbiome across body sites in systemic lupus erythematosus: A systematic review and meta-analysis. Lupus. 2024 Oct;33(12):1345-1357.
  9. Mukhatayev Z, Le Poole IC. Vitiligo: advances in pathophysiology research and treatment development. Trends Mol Med. 2024 Sep;30(9):844-862.
  10. Rai S, Rai G, Kumar A. Eco-evolutionary impact of ultraviolet radiation (UVR) exposure on microorganisms, with a special focus on our skin microbiome. Microbiol Res. 2022 Jul;260:127044.
  11. De Almeida CV, Antiga E, Lulli M. Oral and Topical Probiotics and Postbiotics in Skincare and Dermatological Therapy: A Concise Review. Microorganisms. 2023 May 27;11(6):1420.
  12. Varela-Trinidad GU, Domínguez-Díaz C, Solórzano-Castanedo K, Íñiguez-Gutiérrez L, Hernández-Flores TJ, Fafutis-Morris M. Probiotics: Protecting Our Health from the Gut. Microorganisms. 2022 Jul 14;10(7):1428