Acne is a chronic inflammatory condition associated with a deregulation of the immune system. The pathophysiology of this condition is not totally known, although multiple components are associated [1].
The main causes of acne vulgaris (the most common form) are: excessive sebum production, aberrant proliferation, and differentiation of keratinocytes (a.k.a. cells of our skin) in the hair follicle, bacterial colonization, and host inflammatory reaction [2].
The skin microbiota is a collection of bacteria that live on the skin. They are required for healthy skin function, working with defense systems to prevent bacterial hyperproliferation and colonization by pathogenic strains. When the natural flora is disrupted or the human immune system is compromised, opportunistic bacteria can cause or worsen several skin disorders.
Cutibacterium acnes is an important commensal bacteria of normal skin flora. It is present on the skin's surface and in the sebaceous follicles (sebum-rich environment). In studies that compare healthy and acne patient skins, the amount of C. acnes was found higher in healthy patients. The study also suggests that a loss of equilibrium between C. acnes strains plays a role in acne pathogenesis. The loss of C. Acnes phylotype diversity has been associated with innate immunity activation and skin inflammation in acne, but its mechanism is still unclear [4].
These discoveries point out that treatments that prevent the loss of C. Acnes and thus resolve the dysbiosis seen in acne may help fight this disease. Some clinical trials have demonstrated that topical probiotics can affect the skin microbiota and immune response.
Acne patients treated with topical probiotics have seen a reduction in lesion concentration, erythema, and pathogenic bacterial load, as well as an improvement in the skin barrier. L. Plantarum and cell-free supernatant from E. faecelis were among the probiotics studied [5].
In conclusion, various variables participate in the initiation and maintenance of acne. According to most recent research, topical probiotics may be able to re-establish a more desirable microbiota to reduce acne lesions without causing systemic negative effects.
The relationship between beneficial and pathogenic skin microorganisms and their downstream mediators is diverse and not fully understood. The skin microbiome is unique and varies daily as a result of exogenous and endogenous stimuli. It is unknown why certain people are predisposed to undesirable changes in their skin microbiota [5].
The efficacy of topical probiotics on skin disorders has yet to be thoroughly explored, including clinical trials with bigger samples, to establish the safety, species combinations, dosages, and treatment durations. Future probiotic experiments might produce significant findings to support a microbiome replacement strategy [6].
We can expect in the future more studies to answer the questions regarding the relationship between the skin microbiota and acne, hopefully reaching a new effective treatment and a more complete understanding of this disease.
References
[1] Rocha MA, Bagatin E. Skin barrier and microbiome in acne. Arch Dermatol Res. 2018 Apr;310(3):181-185. doi: 10.1007/s00403-017-1795-3. Epub 2017 Nov 17. PMID: 29147769.
[2] Xu H, Li H. Acne, the Skin Microbiome, and Antibiotic Treatment. Am J Clin Dermatol. 2019 Jun;20(3):335-344. doi: 10.1007/s40257-018-00417-3. PMID: 30632097; PMCID: PMC6534434.
[3] Dreno B, Martin R, Moyal D, Henley JB, Khammari A, Seité S. Skin microbiome and acne vulgaris: Staphylococcus, a new actor in acne. Exp Dermatol. 2017 Sep;26(9):798-803. doi: 10.1111/exd.13296. Epub 2017 Apr 10. PMID: 28094874.
[4] Dréno B, Dagnelie MA, Khammari A, Corvec S. The Skin Microbiome: A New Actor in Inflammatory Acne. Am J Clin Dermatol. 2020 Sep;21(Suppl 1):18-24. doi: 10.1007/s40257-020-00531-1. PMID: 32910436; PMCID: PMC7584556.
[5] Knackstedt R, Knackstedt T, Gatherwright J. The role of topical probiotics in skin conditions: A systematic review of animal and human studies and implications for future therapies. Exp Dermatol. 2020 Jan;29(1):15-21. doi: 10.1111/exd.14032. Epub 2019 Sep 18. PMID: 31494971.
[6] Yu Y, Dunaway S, Champer J, Kim J, Alikhan A. Changing our microbiome: probiotics in dermatology. Br J Dermatol. 2020 Jan;182(1):39-46. doi: 10.1111/bjd.18088. Epub 2019 Jul 28. PMID: 31049923.