After 2 months of use in this randomized double-blind placebo-controlled trial, Lactobacillus paracasei showed a positive effect on skin sensitivity and skin barrier function recovery.
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(2):137-145.
This was a randomized double-blind placebo-controlled trial. Half of the participants were provided with a sachet containing powder of Lactobacillus paracasei, 1x10^10 cfu. The other group was provided a placebo sachet containing the food additive maltodextrin. The study duration was 2 months.
The study included 64 Caucasian women aged 18 to 40 years selected for sensitive skin based on 2 criteria: a validated questionnaire and a positive reaction to capsaicin at low concentration.
Study Parameters Assessed
Assessed were the capsaicin inhalation test, transepidermal water loss, clinical scores, self-assessment, markers of skin hydration (ie, sodium lactate and urea), stool microbiological analysis, interleukin (IL)-10, IL-12, and transforming growth factor beta (TGF-beta).
Primary Outcome Measures
The effects of Lactobacillus paracasei on skin sensitivity and skin barrier function recovery were the primary outcome measures.
Overall trends showed Lactobacillus paracasei had a positive effect on skin sensitivity, skin barrier function recovery, and key associated physiological parameters. The intervention group had higher concentrations of Lactobacillus at study end (day 57). There was statistically significant improvement in perceived skin roughness in the intervention group vs placebo (P=0.006).
Skin reactivity is not a common term in dermatological parlance in the United States. In Europe, it is used to describe patients with what US practitioners refer to as “sensitive skin.” People with sensitive skin report symptoms such as heat, burning, stinging, or itching when exposed to physical (heat, cold, wind) or chemical (topical product application) stimuli.1
Sensitive skin is also characterized by impaired recovery of skin barrier function. Barrier dysfunction leads to increased penetration of irritating substances and transepidermal water loss (TEWL).2
Sensitive skin is common in conditions such as atopic dermatitis, contact dermatitis, psoriasis, rosacea, and urticaria. As such, any intervention that may decrease the sensitivity of the skin in people affected by these conditions would be welcome. The use of a particular probiotic strain is a novel approach to mitigating sensitive skin. This study builds on prior investigations led by two of the authors (Gueniche and Philippe) at their respective positions in the research laboratories of L’Oreal in France and Nestle in Switzerland. They collaborated in this study performed at the Laboratoire Dermscan in Lyon, France.
Earlier research had shown that Lactobacillus paracasei NCC 2461(ST11) modulates immune homeostasis and downregulates immune-related disorders.3 Gueniche had demonstrated that a medium conditioned with ST11 significantly reduced substance P–induced vasodilation, edema, mast-cell degranulation, and tumor necrosis factor release, and also promoted recovery and maintenance of skin barrier function.4 Philippe had confirmed this finding in vivo.5
The present study revealed that participants given ST11 had a slight but significant decrease in skin sensitivity to capsaicin over the treatment period. Barrier function recovery measured as decreased TEWL was significantly faster in subjects supplemented with ST11 compared to the placebo group. These results suggest 3 potential mechanisms underlying the effect of this probiotic on skin sensitivity:
- inhibition of the release of neuromediators,
- decreased neurogenic inflammation, and
- improvement in skin barrier function.
A fourth mechanism may be an interaction between the probiotic and gut mucosa–associated immune system,6 involving the release of cytokines (eg, TGF-beta) into the blood that may reinforce or restore skin homeostasis and integrity.
We are at the cusp of a much more sophisticated understanding of the therapeutic applications of probiotics, not only for skin disease but for a great number of immune-mediated conditions.
Markers of some components of the natural moisturizing factor of the skin were measured (ie, sodium lactate and urea). These markers remained unchanged in subjects taking ST11 and decreased in those taking placebo. These results correlated with a significant improvement in facial skin roughness (P=0.006) and a similar trend (P=0.08) for leg skin dryness in participants given ST11 compared to those given placebo. Subjects supplemented with ST11 also showed significantly higher levels of TGF-beta compared to the control group.
Stool analysis revealed that 1 week after completing the study, ST11 was found in only 10% of the subjects, indicating ST11 had a very limited ability to persist in the intestine.
A recent review article described the beneficial effects of Lactobacillus paracasei subsp. paracasei NTU 101, including management of hyperlipidemia, hypertension, gastric mucosal protection, allergic disease, osteoporosis, and obesity.7
In the past several years, there has been intense research interest in the use of probiotics for many diseases, including skin disorders such as atopic dermatitis, psoriasis, acne, and rosacea.8-11 Many questions remain, including the issue of dosage. A recent review summarizes the current knowledge on the effective dosage of different probiotic strains used for several disorders.12
This study by Gueniche and Philippe provides an important reminder to the clinician about the contribution of gut health to skin disease. Their results reinforce the concept of an inside-out, outside-in approach to the treatment of common skin disorders such as atopic dermatitis, psoriasis, and acne. In order to provide comprehensive care to patients with sensitive skin, probiotic strains should be selected with proven benefit for these conditions and ideally prescribed at proven-effective dosages. We are at the cusp of a much more sophisticated understanding of the therapeutic applications of probiotics not only for skin disease but for a great number of immune-mediated conditions that are intimately tied to the fact that the vast majority of our immune system is located in the gut.
Despite controlling for many potentially confounding variables―such as fermented milk products, systemic medications that could affect inflammatory responses, intestinal surgery, vegetarian diet, and nutritional supplements―it would have been interesting to see if adjustment for dietary behaviors and/or patterns would have affected the results of this study (specifically, in regards to other fermented foods such as sauerkraut, cheese, pickles, tofu, tempeh, miso, and kombucha).