Understanding the Microbiome

By Piroska Cavell / 14 Sep 2022

Nurse prescriber Piroska Cavell investigates the relationship between the gut and skin health

The connection between the skin and the gut microbiome is a relatively new discovery, but it has a substantial impact on treating the skin to improve quality, treat disease or reduce the effects of ageing, including photoageing and environmental damage.

In my experience, patients are also becoming increasingly aware of this and are actively looking for a more holistic approach to their skincare and aesthetic treatments. It is important for practitioners to keep up to date with not only medical advances, but also the increased awareness patients have with regards to their knowledge of treatments and their health. 

What is the microbiome? 

The microbiome is the collective term used to describe the entire environment surrounding the variety of diverse micro-organisms that create a particular habitat, including within the gut and on the skin.3 Microbiota refers specifically to a group of elements that are biota only – live bacteria that have a positive effect on the body and can be introduced to the body without causing harm, such as the microbe Lactobacillus.3 It can be confusing as the terms microbiome and microbiota are very often used interchangeably. 

There are millions of diverse organisms within a microbiome that co-exist with the host (in this case humans) without harming it. These include microbes, fungi and protozoa. The microbiome contains more than 10 times the amount of host cells with 150 times more genetic material. Their functions include the secretion of p40 protein to supress cytokine-mediated apoptosis and epithelial cell interference, and they have been shown to have both immune and neurotransmitter properties.4 The microbiota is capable of actively killing pathogens, reinforcing the epithelial barrier and skin, induction of fibroblasts and epithelial cell migration and function.

What can affect the gut microbiome? 

The delicate balance of the gut microbiome is suspectible to disruption by medication such as antibiotics, malnutrition, stress, disease, dehydration, high alcohol and caffeine intake, a diet high in processed food, processed carbohydrates and a lack of fibre.5 Research, such as that conducted by Kim et al. clearly demonstrates the effect of a disruption in the gut flora.6 The disruption triggered the production of over-regulatory T cells, leading to the development of autoimmune disorders and reduction in the protection against inflammatory disorders including arthritis. They also evidenced how gut microbiome dysbiosis had a stimulating effect on metabolic neurodegenerative neoplastic disease.

Gut microbiome and skin health 

The microbiome of the gut has a far-reaching effect beyond the gastro-intestinal system, influencing other organs including the skin. Both the skin and the gut have a unique microbiome crucial to the maintenance of the health of each independently, moderating and monitoring what is taken into and absorbed through them. Both have vital immunological functions related not just to themselves but to systemic function, and are essential to the continuation of physiologic homeostasis.6 It is now widely accepted that the skin and gut microbiomes communicate with each other, influencing inflammatory and immune responses within the body. Together, they form the skin-gut axis.

The gut and skin floras’ constant bi-directional communication is through mediation and modulation of adaptive and innate immunity, mainly by the gut microbiota which contains 70% of the body’s immune cells.6 This is how these respective systems collaboratively rectify and preserve allostasis, as well as maintain homeostasis of the skin and the gut, and thus the health and optimum function of the whole body too. The skin microbiome also performs an immune function as part of maintaining skin homeostasis, but not to the same extent as the gut. Like the gut, the skin has a dense colonisation of bacteria, an overgrowth of which is commonly found in several skin diseases.

Current research 

Early evidence that the gut microbiome has an influence on the skin was reported by a pivotal study in which mice were given drinking water enhanced with the addition of Lactobacillus reuteri.2 The mice developed a thickened epidermis, as well as an increase in acidity of the epidermis, follicular genesis and sebocyte production. This led to thicker, shinier and healthier fur. These changes were found to be linked to an immune system response triggered by the added bacteria. Later, a randomised control double-blind placebo-controlled trial study on two sets of groups of 32 humans showed reduced skin sensitivity and reduced transepidermaltrans epidermal water loss from the skin, after patients were given Lactobacillus paracasei NCC2461. 

In addition, Kosiewicz et al. identified that racteroides fragilis, faecalibacterium prausnitzii and clostridium cluster IV and XI bacteria produce retinoic acid and polysaccharide, which stimulates the anti-inflammatory response with the accumulation of regulatory T cells.

O’Neil et al. discovered that disrupted intestinal barriers allow gut metabolites and microbiota to access the circulatory system in the skin and disrupt cutaneous homeostasis.2 This disruption can be treated with the ingestion of oral probiotics to modulate the gut microbiota, triggering the anti-inflammatory response at the cutaneous level.

In 2006 Baba, Masuyama and Takana published their experiments with Lactobacillus helveticus fermented milk and its effects on normal human epidermal keratinocyte differentiation.8 Results showed the fermented milk stimulated keratinocyte differentiation, promoting the expression of profilaggrin at mRNA level which in turn becomes filaggrin – a natural moisturiser in skin. In dry skin it is at negligeable levels or in conditions such as itchthyosis vulgaris and contact dermatitis absent. 

They concluded that Lactobacillus helveticus fermented milk was expected to be a useful moisturising agent for treating dry skin by boosting filaggrin production. They also demonstrated how Lactobacillus helveticus had a positive effect on the reduction of the severity of sodium dodecyl sulphate induced dermatitis.8 In their open label trial with 101 female participants, Mori et al. showed that Lactobacillus paracasei can reduce skin inflammation, with certain conditions all showing significant improvement, if not total resolution, when patients are treated with pre-and probiotics.

Gut health and skin conditions 

The pathophysiology of acne vulgaris is influenced by the bi-directional cross-communication between the gut and skin microbiota. This condition is more prevalent in western societies, and is linked to a diet high in carbohydrates.10 This high intake of carbohydrates stimulates insulin/insulin-like growth factors, leading to a process ultimately triggering the target for rapamycin factor 1 – a controller of metabolism and proliferation of cells. It mediates lipogenesis, hyperproliferation of sebaceous glands and hyperplasia of acroinfundibular keratinocyte, therefore playing a role in the development of acne. Gastrointestinal disorders and disruption of the gut membrane, triggering malabsorption of minerals such as chromium, zinc and selenium, have been shown to further influence the psychological state of patients, and with oxidative stress, have been linked to acne vulgaris.10

 Likewise, hypochondria has been linked to acne due to reduced acidity allowing the migration of colonic bacteria to the small intestine, causing small intestine bacterial overgrowth and triggering gut dysbiosis. This ultimately leads to systemic inflammation.10 

Psoriasis is often linked with inflammatory bowel disease, with 11% of patients suffering from both conditions. It is known that psoriasis is linked to gastrointestinal inflammation and inflammatory conditions of other organs. Patients with psoriasis have had intestinal bacteria DNA isolated in their blood plasma.10 

There are also strong connections between gut health and eczema and rosacea, but detail on this is outside the scope of the article. 


As discussed here, there are marked similarities between the gut and the skin. In light of the above, my ethos has always been to take a holistic approach with patients. I talk a lot about the mind, body connection, the interaction of all the organs and the effects of diet and nutrition on skin health, ageing and appearance. Included in the consultation is a discussion about the patient’s diet. I explain the link between what patients put into their body and the condition of their skin. During this discussion, it is easy to enable patients to relate to the connection between their diet and their skin by asking simple questions such as: Have they ever had a breakout when they have eaten a lot of junk food? Had a little too much alcohol? Or when taking certain types of medication, especially antibiotic therapy? We also discuss stress levels and their emotional state and explore how their nutrition can influence their mood with a move to a more natural, low-sugar diet. 

In addition, I recommend adding supplements such as lactobacillus and fermented foods which support gut health and rebalance the microbiome, helping to maintain homeostasis and the control of inflammation. This contributes to healthy, optimum functioning skin.9 

Alongside this, the right skincare is essential. I recommend using skincare that is formulated with ingredients from the local coast such as bio kelp or marine algae, and including probiotic serums for the face and body. These products work with the skin, rather than disrupting the skin’s natural microbiota, rebalancing the skin microbiome.11 

A holistic approach 

In recent years, a greater understanding of the importance of the microbiome in the gut and its systemic influence on the body is being recognised in medicine and is more widely acknowledged as a target for treating a variety of conditions, including several relating to the skin. With ongoing research into what is viewed as a new area of medicine, and in light of the increase in antibiotic resistance, this is being seen as a potential significant alternative. Practitioners should take a holistic approach to treating patients, establishing whether their diet and nutrition is affecting their skin health and recommending solutions accordingly. 

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