"The Crossroads between a Healthy Gut and Clear Skin: A Narrative Review of Probiotics and the Gut-Skin Axis in the Pathogenesis and Management of Acne Vulgaris" by Syed Arif

The Crossroads between a Healthy Gut and Clear Skin:

A Narrative Review of Probiotics and the Gut-Skin Axis in the Pathogenesis and Management of Acne Vulgaris

Syed Arif, Fairleigh Dickinson University

Abstract: Acne, or acne vulgaris, is an extremely common multifactorial skin disease that often affects a large portion of adolescents and young adults across the world. The root causes of acne include the overproduction of sebum, follicular obstructions, bacterial and fungal overgrowth, and inflammation (Garrick, 2016, p. 1). Luckily, of the people who experience acne, most suffer from mild symptoms while only about 20% are exposed to more severe symptoms that can cause facial scarring on top of permanent psychological conditions like depression and anxiety (Zaenglein, 2018, p. 10). Although topical retinoids, antibiotics, and hormonal therapies can have varying levels of success in those with severe acne, the use of these medications is not without serious side effects, like antibiotic resistance, skin irritation, and hormonal imbalance. This has led to the search for an alternative therapy that can effectively rebalance the body’s microbiota in order to manage and improve acne. Among all the treatments that have been considered in the past decade, the most promising is the use of probiotics, which are the live microorganisms that—in proper doses—can restore healthy skin and prevent the root causes of acne from manifesting. Increasing data indicate that probiotics, via interactions with the gut microbiota, may help in the control of acne by altering systemic inflammation, immune response, sebum secretion, and skin microbiota homeostasis. As a result, this paper posits that probiotics could reduce acne and can possibly be used as an acne treatment alongside or instead of the standard topical and oral treatments.

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Pathophysiology of Acne

Acne formation and proliferation are a result of multiple factors. Sebum, an oily substance secreted by sebaceous glands, blocks the hair follicles and is involved in the formation of acne as it creates an environment for Propionibacterium acnes (P. acnes) bacteria to grow. These bacteria cause inflammation in the body and skin and thus form pimples, cysts, and other skin lesions on the skin surface (Mclaughlin, 2019, p. 2). Additionally, hormone imbalances caused by entering puberty, menstruation, and pregnancy can also cause an increase in sebum production, which worsens acne. As such, the main reasons for the development of acne are hormones, sebum, and inflammation. Diet and genetics are known to cause acne as well; however, those components often contribute indirectly by raising inflammation or changing the skin’s microbiome.

The Gut Microbiome and Systemic Inflammation

Of the proposed mechanisms through which probiotics can help to reduce acne, one of the most important is the modulation of systemic inflammation. Research has indicated that people with acne have a higher concentration of pro-inflammatory cytokines—immune cells that send out signals for inflammation—such as tumor necrosis factor-alpha, interleukin-6, and interleukin-8 (Bowe, 2011, p. 441). These cytokines are proinflammatory molecules, and the development of acne lesions in patients with Acne vulgaris is already strongly associated with inflammation. When probiotics are introduced, they can modulate the immune response through the production of anti-inflammatory cytokines like interleukin-10, which suppress pro-inflammatory cytokines like necrosis factor-alpha (Németh, 2019, p. 14). Lowering the levels of pro-inflammatory cytokines while raising levels of anti-inflammatory cytokines ultimately lowers inflammation in all body tissues, including the skin. What this means is that the symptoms of acne that stem from inflammation can be somewhat reduced by simply taking more probiotics.

The gut microbiome plays a crucial role in managing acne, as it influences immunity, metabolism, and inflammation. Gut dysbiosis is associated with many chronic diseases, such as acne (Rosenblat, 2020, p. 185). The gut microbiome regulates the immune system, and disruption of the normal gut flora leads to increased permeability of the intestinal barrier through which inflammatory molecules and bacteria enter the circulation and cause systemic inflammation. This means that by diversifying your nutrition or by taking a probiotic supplement to fill in the gaps of a lackluster nutrient profile, one can prevent or reverse dysbiosis via introducing healthy bacteria that support the immune system, support the integrity of the gut lining, and reduce inflammation. Consequently, the restoration of bacterial balance in the gut helps to reduce acne severity by preventing inflammation caused by dysbiosis that would eventually lead to the development of acne (Dreno, 2020, p. 1).

Hormonal Regulation via Probiotics

Besides modulating systemic inflammation, probiotics can also impact sebaceous glands, which are a major factor in the pathogenesis of acne. Hormonal changes, which are common during puberty, pregnancy, and the menstrual cycle, all cause an increase in sebum production (Ghosh, 2014, p. 1). This excess oil creates an environment where P. acnes bacteria are able to grow with ease and thus worsens acne symptoms. Probiotics may have an indirect impact on sebum levels by improving liver function and hormone balance. Some of the probiotic strains, including Lactobacillus acidophilus, have been found to affect hormone metabolism in the liver, where hormones are detoxified before they are excreted. This includes hormones known as androgens, which are responsible for stimulating the sebaceous glands (Shah, 2024, p. 1). Since probiotics control the secretion of hormones and regulate androgen production, it can indirectly be used to control the secretion of sebum, preventing the formation or worsening of acne.

The Skin Microbiota and Topical Probiotics

The skin microbiota comprises a vast number of microbes and is the primary cause of acne that can be managed with topical probiotics. In acne, the skin microbial community is disturbed, and the number of P. acnes increases while other skin commensal bacteria are suppressed. The positive effect of probiotics can be explained by the ability to enhance the growth of beneficial bacteria while suppressing the microbial flora that causes acne (Kim, 2018, p. 1). Kim's research stated that the application of topical probiotics was able to help reduce acne symptoms by rebalancing the skin microbial environment. This means that probiotics can be a useful treatment against acne, not only internally but also externally. Topical probiotics were shown to help restore the skin microbiota by decreasing the colonization density of P. acnes and bringing the skin microbial community back to a state of homeostasis (Kim, 2019, p. 4). This localized effect may result in fewer numbers of acne lesions and less severe forms of acne. Consequently, the application of topical probiotics can reduce the development of acne to some extent, suggesting probiotics can be a promising complementary treatment for stubborn acne.

The Gut-Brain-Skin Axis

The gut-brain-skin axis is one more route through which probiotics can affect acne. The gut-brain axis is defined as the interaction between the gut and the brain involving the vagus nerve, hormones, and immune signaling (Carabotti, 2015, p. 1). Stress is known to cause acne, and studies have confirmed that stress causes cortisol levels to rise, leading to inflammation and elevated sebum production. Probiotics may help to reduce the effects of stress on acne by influencing the gut-brain axis and reducing the stress response. One research study examined the effects of probiotics on stress and acne, revealing that patients who received probiotic supplements noticed better scores in acne and perceived stress (Mays, 2017, p. 132). This indicates that probiotics could aid in the alleviation of acne-related problems both by reducing psychological stress and by directly controlling the physiological factors that lead to acne formation. Thus, probiotics may become a comprehensive solution to acne and, apart from the external symptoms, help to eliminate the psychological and emotional factors that exacerbate the condition, such as stress.

Dietary Probiotics and Nutritional Modulation

A diet of probiotic-containing foods can modulate the severity of acne. Probiotic foods like yogurt, kefir, kimchi, sauerkraut, and others are packed with good bacteria that help to strengthen the gut and the immune system. Research has established that these foods, when taken in proper doses, can help maintain the composition of the gut bacteria, which is especially important for digestion and immune function, but also the development of acne as previously established (Neufeld, 2016, p. 142). Probiotic-rich foods contain vitamins, minerals, and antioxidants, which help to prevent skin damage through reducing oxidation and inflammation—the main factors in acne formation. Thus, consuming foods that promote the growth of good bacteria may complement the use of probiotics and therefore offer extra shielding against acne. Fiber-rich diets, for instance, are known to increase the population of friendly bacteria in the gut and reduce the population of pathogenic bacteria that may lead to acne. Likewise, limiting inflammatory foods, which include sugar and dair,y can help decrease acne outbreaks (Bowe, 2011, p. 441). When probiotics are combined with prebiotics (fiber) and anti-inflammatory foods, the results may be even stronger in terms of acne and skin condition. As such, following a diet high in probiotic-containing foods offers similar benefits to taking probiotic supplements as they relate to treating acne.

Diverging Findings and the State of Research

Despite the promising results of probiotics in acne treatment, there are certain issues and limitations that should be considered. One major limitation is the heterogeneity of the effects of probiotics in the human population. Each person has their own gut microbiota, and the effects of probiotics are highly dependent on individual characteristics, including genetic, diet, lifestyle, and environmental factors. Therefore, probiotics’ efficacy in acne treatment may be variable, and further studies should aim at defining the best strains suitable for particular phenotypes of acne (Rosenblat, 2020, p. 185). An example of heterogeneity within the current state of research can be seen when comparing major studies reporting the effect of probiotics on systemic inflammation. Németh (2019) and Di Marzio et al. (2003), for instance, demonstrated that anti-inflammatory cytokines like interleukin-10 (IL-10) and Lactobacillus plantarum, respectively, could inhibit pro-inflammatory responses, thereby reducing overall systemic inflammation. This, however, is contrary to the findings of a randomized controlled trial by Kim et al. (2019) involving Lactobacillus fermentum, which failed to show statistically significant reductions in systemic inflammatory markers despite improvements in acne lesion counts. Such inconsistencies in the literature often stem from differences in probiotic strains used, dosages, treatment durations, and patient-specific factors such as microbiome composition or diet. Thus, while there is growing evidence that probiotics can influence immune signaling relevant to acne pathogenesis, further standardized and strain-specific research is needed to establish clear clinical guidelines. Future researchers should also compile data more meticulously to answer which strains of probiotics are most effective, as well as what amount and length of time is ideal in probiotics’ usage as an acne treatment.

A secondary drawback in using probiotic treatments is their potential side effects, especially in patients with weakened immune systems. Patients with autoimmune diseases, cancer, or those on immunosuppressive drugs may be more susceptible to infections resulting from live bacteria (Gänzle, 2015, 134). Therefore, people in these groups should seek advice from their health care provider before taking any probiotic treatments. A tertiary and lesser, but still prevalent, issue is that some people may develop an upset stomach, bloating, or gas while using probiotics. These side effects, however, tend to reduce as one continues to take the supplements and their gut becomes accustomed to the treatment. Further research must be done on the specific drawbacks of probiotic supplementation before they can confidently be used alongside or in replacement of existing acne treatments.

Conclusion

Ultimately, probiotics can be considered as a complementary therapy to the conventional treatments of acne. In addition to controlling the levels of inflammation, regulating seborrhea, rebalancing the gut and skin microbiota, and even affecting the communication between the gastrointestinal tract and the nervous system, probiotics may be an effective and comprehensive approach to stubborn acne. Emerging clinical trial data suggest that probiotics are effective in the management of acne vulgaris and the severity and frequency of outbreaks in persons where inflammation or microbial dysbiosis are the key drivers of the condition. Further work is required to establish ideal strains, doses, and treatment durations, but the possibility of using probiotics as a safe, non-pharmacological, and effective acne therapy is promising. Based on research and development in the field of microbiome science, probiotics may eventually become a replacement or integrate into traditional acne treatments, marking a promising crossroads for the bilateral improvement of both gut and skin health.

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