Acne is primarily attributed to hormonal changes but it may also be associated with a specific skin microbiota, which is likely influenced by the gut-brain-skin axis.
Acne affects around 80% of adolescents, of whom 15% will have severe acne, and almost 25% of adults, particularly women. It is characterized by an increased secretion of sebum and keratinization disorders, which result in obstruction of the hair follicle. This promotes the proliferation of Propionibacterium acnes and causes inflammation.
The role of skin microbiota
Acne combines different kinds of lesions, whose forms depend on the nature of the skin and hormonal changes. However, changes in the skin microbiota have also largely been implicated1 . Acne has been associated with a specific skin microbiota, with an overrepresentation of Propionibacterium acnes in the sebaceous glands and hair follicles, but also with Staphylococcus epidermidis2,3. Current studies are focusing on this microbiota and the virulence factors produced by these bacteria.
The gut-brain-skin axis
This skin dysbiosis may also be the result of disruptions in the “gut-brain-skin axis.” This hypothesis has been the subject of sustained interest for more than 80 years4. Studies have shown, for example, that the intestinal microbiota modulates the secretion of substance P by the nervous system, which acts, among others, on the skin5. Research is constantly going in that direction because of the following factors: high incidence of psychological disorders (stress, anxiety) in people affected by acne, higher rate of functional intestinal disorders in these patients, and increased blood lipopolysaccharide levels1 .
Probiotics under study
To date, treatments have relied on topical therapies and a healthy lifestyle. New avenues for treatment of acne also involve probiotics. Several randomized controlled trials have shown the effectiveness of several strains of lactobacilli in humans, with beneficial effects on the skin barrier, sensitivity, hydration, and functions of the epidermis6,7,8 . Studies have been carried out on the treatment of acne with Lactobacillus acidophilus and Lactobacillus paracasei4.
1. Bipul Kumar et al. New insights into acne pathogenesis: Exploring the role of acne-associated microbial populations. Dermatologica sinica June 2016Volume 34, Issue 2, Pages 67–73
2. Wang Y et al. Staphylococcus epidermidis in the human skin microbiome mediates fermentation to inhibit the growth of Propionibacterium acnes: implications of probiotics in acne vulgaris. Appl Microbiol Biotechnol. 2014 Jan;98(1):411-24
3. Christensen GJ et al. Antagonism between Staphylococcus epidermidis and Propionibacterium acnes and its genomic basis. BMC Genomics. 2016 Feb 29;17:152
4. Bowe W et al. Acne vulgaris, probiotics and the gut-brain-skin axis: from anecdote to translational medicine. Benef Microbes. 2014 Jun 1;5(2):185-99
5. Bercik P et al. The intestinal microbiota affect central levels of brain-derived neurotropic factor and behavior in mice. Gastroenterology 2011 ; 141 : 599-609. https://www.ncbi.nlm.nih.gov/pubmed/21683077
6. Peguet-Navarro J, Dezutter-Dambuyant C, Buetler T, et al. Supplementation with oral probiotic bacteria protects human cutaneous immune homeostasis after UV exposure-double blind, randomized, placebo controlled clinical trial. Eur J Der- matol 2008 ; 18 : 504-11.
7. Gueniche A, Philippe D, Bastien P, et al. Randomised double-blind placebo-controlled study of the effect of Lactobacillus paracasei NCC 2461 on skin reactivity. Benef Microbes 2014 ; 5 : 137-45.
8. Philippe D, Blum S, Benyacoub J. Oral Lactobacillus paracasei improves skin barrier function recovery and reduces local skin inflammation. Eur J Dermatol 2011 ; 21 : 279-80.