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The inflammatory origin of psoriasis remains mysterious. Study results showed microbiota changes in these patients.

Psoriasis affects around 2% of the population, at all ages. It is characterized by chronic skin inflammation. It appears in people who are genetically predisposed with physical or psychological factors facilitating its onset. This inflammation leads to uncontrolled proliferation of epidermal cells, with keratinocytes being replaced in 3 days instead of 28, and the cells have anomalies. Moreover, 20% of the patient also have painful joint involvement1.

A disrupted  intestinal microbiota

The origin of the inflammation remains unknown, but researchers have detected differences between the intestinal microbiota (gut flora) of healthy subjects, and those of people with psoriasis alone or psoriasis and arthritis. That observation suggests a potential microbiota role in the cutaneous lesions and arthritis onset2

Different dysbioses in the presence of arthritis

The intestinal microbiota of psoriasis patients is less diverse and less rich in Coprococcus2. In those who also have arthritis, Ruminococcus and Akkermansia muciniphila are less represented, like in patients with chronic inflammatory bowel diseases2. Ongoing research is trying to determine whether the intestinal microbiota anomalies precede arthritis onset, which could help to screen at-risk subjects and might suggest a causal relationship2.

Local and systemic treatments

Depending on its severity, psoriasis is based on topical agents (steroids, vitamin D3 analogues) and phototherapy, or systemic molecules (retinoids, methotrexate, cyclosporine and biopharmaceuticals). Current studies are investigating the impact of probiotics on localized cutaneous inflammation and dysbiosis.


1. Société Française de dermatologie.
2. Scher JU et al. Decreased bacterial diversity characterizes the altered gut microbiota in patients with psoriatic arthritis, resembling dysbiosis in inflammatory bowel disease. Arthritis Rheumatol 2015;67:128-39. 

Atopic eczema

There seems to be a complex interaction between the cutaneous immune system and the microbiota which plays a role in the appearance of atopic eczema. Its modulation with probiotics is a promising avenue as a preventive measure.

Atopic eczema, more commonly called atopic dermatitis, can affect up to 25% of children and 7% of adults in industrialized countries. This allergic affliction manifests itself in the form of dryness and cutaneous lesions, progressing by flares: redness, itching, blisters, and scabs1

Genetic and environmental factors

Dermatitis is related to a genetic predisposition that causes structural anomalies in the skin, as well as immune system hyperreactivity. Between 50% and 70% of patients who suffer from atopic dermatitis have a first-degree relative with the disease. Environmental factors are also suspected of changing the balance in the immune system1

Gastrointestinal microbiota associated with atopy

The intestinal and cutaneous microbiota seem to contribute to the affliction, although the mechanisms are not clearly established. Several studies have shown a link between the intestinal microbiota and the allergy2, with changes in the former, for example, before the appearance of an atopic syndrome3. Dysbioses are also present in the cutaneous microbiota4. There are likely connections between the intestinal and cutaneous microbiota through the passage of bacteria from one tissue to another, or through interrelationships with other organs like the immune system and the brain5,6,7,8

Probiotics are extremely promising

Standard treatment of atopic dermatitis flares is based on the use of topical steroids, or topical immunomodulators for the most severe cases. Phototherapy has also been proven effective. 
Current research is directed towards correcting dysbioses as a preventive measure. The neonatal period seems particularly opportune to induce effective immunomodulation and reduce the risk of atopic eczema. A meta-analysis showed that the administration of probiotics like Lactobacillus rhamnosus GG to pregnant women seems promising to prevent atopic dermatitis in children9. Furthermore, several studies have shown the usefulness of Lactobacillus salivarius in treating atopic dermatitis in adults and children10,11.

1.     Société française de dermatologie,
2.    Candela M, Rampelli S, Turroni S, et al. Unbalance of intestinal microbiota in atopic children. BMC Microbiol 2012 ; 12 : 95. 
3.    Penders J, Thijs C, van den Brandt PA, et al. Gut microbiota composition and development of atopic manifestations in infancy: the KOALA Birth Cohort Study. Gut 2007 ; 56 : 661-7. 
4.    Dereure. Microbiome cutané et dermatite atopique : un second génome ? Réalités pédiatriques février 2015 ; 191 : 43-45
5.    Findley K, Grice EA. The skin microbiome: a focus on patho- gens and their association with skin disease. PLoS Pathog 2014 ; 10 : e1004436. 
6.    Collins SM, Bercik P. Gut microbiota: Intestinal bacteria influence brain activity in healthy humans. Nat Rev Gastroen- terol Hepatol 2013 ; 10 : 326-7.

7.    Bowe WP, Patel NB, Logan AC. Acne vulgaris, probiotics and the gut-brain-skin axis: from anecdote to translational medicine. Beneficial Microbes 2014 ; 5 : 185-199. 
8.    Arck P, Handjiski B, Hagen E, et al. Is there a “gut-brain-skin axis”? Exp Dermatol 2010 ; 19 : 401-5.

9.    Pelucchi C, Chatenoud L, Turati F, et al. Probiotics sup- plementation during pregnancy or infancy for the prevention of atopic dermatitis: a meta-analysis. Epidemiology 2012 ; 23 : 402-14. 

10.    Drago L. et al. Effects of Lactobacillus salivarius LS01 (DSM 22775) treatment on adult atopic dermatitis: a randomized placebocontrolled study. Int J Immunopathol Pharmacol. 2011;24:1037-48.
11.    Niccoli AA. et al. Preliminary results on clinical effects of probiotic Lactobacillus salivarius LS01 in children affected by atopic dermatitis. J Clin Gastroenterol. 2014;48 Suppl 1:S34-6.


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.
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.


  • Rheumatoid arthritis

  • Allergics

  • Cardiovascular pathologies

  • Gyneco

  • Pulmonary pathologies

  • Psychiatric and Neurodegenerative

  • Urinary


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