The skin serves as a critical barrier against external threats—dehydration, ultraviolet exposure, and infections—playing a significant role in internal homeostasis and moisture retention. Additionally, and equally importantly, it interacts dynamically with the complex microbiome resident in it, which is essential for maintaining skin health. Recent interest has focused on the use of probiotics and postbiotics, besides their ability to modulate the skin microbiome, to enhance barrier function, and exhibit anti-inflammatory properties, to be involved in skincare, by having the potential to improve skin hydration, elasticity, and overall appearance, as well as in reducing signs of aging, such as wrinkles and fine lines. The products—being a combination of a cosmetic regime plus probiotic[s] or postbiotic[s]—are named cosmeceuticals. However, to comply with the regulations for the characterization of a microorganism as a specific probiotic strain, the pro- or postbiotics incorporated into the cosmetic regime should be both genetically and phenotypically defined. Thus, in this review, we present 14 published clinical trials using such cosmetic products with specific, well-characterized strains of probiotics or postbiotics applied to volunteers with healthy skin. Looking at the results of these studies collectively, we can say that these genetically and phenotypically defined strains of either live or inanimate bacteria and/or their components seem to keep the treated skin at least fully hydrated, with intact epithelial tone, increased radiance, and with decreased wrinkle depth, while normalizing the commensal skin microbiota. Future advancements in personalized skin care may lead to genomic sequencing and metabolomics to tailor probiotic and postbiotic treatments to individual skin microbiomes, promising a new frontier in cosmeceuticals.

Background: Psychological disorders are prevalent in patients having undergone gastrointestinal cancer surgery, and their emotional status may further deteriorate during subsequent chemotherapy. Psychobiotics are specific probiotics that have the unique characteristics of producing neuroactive substances that are thought to act on the brain–gut axis. The aim of the present study was to evaluate the benefits of a psychobiotic formula on depression and anxiety status, as well as on perceived stress, versus a placebo in patients on a chemotherapy course following gastrointestinal surgery for cancer. Patients: The enrolled patients, allocated to the psychobiotic and placebo groups, were assessed by means of these psychometric tests: Beck’s Depression Inventory and the Hamilton Depression Rating 17-item Scale for depression; the General Anxiety Disorder-7 for anxiety; and the Perceived Stress Scale-14 Item for perceived stress at three time-points: upon allocation [T1], after one month of treatment [T2], and two months thereafter [T3]. Results: In total, 266 patients were included. One month of psychobiotic treatment improved [i] depression status by 60.4% [48 depressed patients at T1, reduced to 16 at T3]; [ii] anxiety by 57.0% [72 patients at T1, 26 at T3]; and [iii] stress by 60.4% [42 at T1, 14 at T3]. The placebo-treated patients experienced a deterioration in all parameters studied, i.e., depression increased by 62.9%, anxiety by 39.7%, and stress by 142.5%. Conclusions: Based on these findings, it can be recognized that psychobiotic treatment has great potential for every patient at risk of suffering from depression, anxiety, or stress during the course of surgery/chemotherapy for gastrointestinal cancer.

Background: Depression is a leading contributor to global disability, with a large proportion of patients showing inadequate responses to conventional antidepressants. Probiotic bacteria with psychotropic potential seem to be an emerging treatment option, either alone or in conjunction with depression symptom management. Objective: To critically review the Randomized Clinical Trials (RCTs) whose primary focus was to evaluate the efficacy of probiotics/psychobiotics to ameliorate depression status, quantified via validated psychometric tools. Methods: A comprehensive literature search of the PubMed and Scopus databases (January 2014–January 2025) was conducted to identify RCTs with the primary aim of improving depression status in adults taking probiotics in comparison to those taking a well-defined placebo. Results: Nineteen RCTs met the inclusion criteria, with all demonstrating a significant amelioration of depression status after probiotic/psychobiotic treatment, taken either as a stand-alone treatment [n = 5] or as an adjunctive treatment to antidepressant therapy [n = 10]. However, only in 14 studies was a significant improvement achieved at the end of treatment over a placebo, which also showed an improvement against the baseline. In total, 7 out of 10 studies with probiotics as an add-on therapy and 7 out of the 9 with probiotics, either as a monotherapy or with a different percentage also taking antidepressants, exhibited a significant amelioration of depression status against placebo treatment. Conclusions: Probiotics, particularly multi-strain preparations and certain well-characterized single strains, seem to be noticeably beneficial in alleviating depressive symptoms in adults. However, there is an urgent need for large-scale randomized clinical trials with well-defined specific psychobiotic strains in order to confirm the most effective strains.

Background: Since the consensus of ISAPP on the definition of the term “postbiotic” there has been an enthusiasm for publications in review form—their number being disproportionate to the primary research. The aim of this bibliometry is to analyze the bibliometric trends of this newfound interest in the field. Methods: Search of the PubMed database for review articles on postbiotics, published between November 2021 and June 2024. Results: Analysis was performed on 92 review articles, the number corresponding to 2.9 reviews per month. China, Poland, Italy, Iran and India had the maximum productivity among the 32 countries involved; 21 articles were published in 13 journals with the highest impact factor, while 45 were in 16 journals with an IF between 4.0 and 4.9. The authors were mainly affiliated to universities with specialization in both basic research and technology, as well as food science. The top five publications regarding the citations received, published in Foods (2), EBioMedicine, Biomolecules, and Front. Nutr., have collected between 138 and 109 citations. Conclusions: The ever-growing number of reviews regarding postbiotics is perhaps disproportionate to the actual original research in the field. Further clinical trials would extend and deepen the subject and facilitate the drowning of more robust conclusions in relation to their effects.

Background: Pain is a multifaceted and debilitating symptom in patients with gastrointestinal cancer, especially those undergoing surgical resection followed by chemotherapy. The interplay between inflammatory, neuropathic, and psychosocial components often renders conventional analgesia insufficient. Psychobiotics—probiotic strains with neuroactive properties—have recently emerged as potential modulators of pain perception through neuroimmune and gut–brain axis pathways. Methods: This post hoc analysis is based on the ProDeCa randomized, placebo-controlled trial, which originally aimed to assess the psychotropic effects of a four-strain psychobiotic formulation in postoperative gastrointestinal cancer patients receiving chemotherapy. In the current analysis, we evaluated changes in pain perception among non-depressed and depressed participants, who received either psychobiotics or placebo, along with standard analgesic regimes. Pain was assessed at baseline, after a month of treatment, and at follow-up, 2 months thereafter, using the Short-Form McGill Pain Questionnaire (SF-MPQ), capturing both sensory and affective components, as well as with the Present Pain Intensity and the VAS scores. Results: Psychobiotic-treated participants—particularly the non-depressed ones—exhibited a significant reduction in both quantitative and qualitative pain indices over time compared with placebo-treated ones. Improvements were noted in total pain rating index scores, sensory and affective subscales, and present pain intensity. These effects were sustained up to 2 months after intervention. In contrast, placebo groups demonstrated worsening in pain scores, probably influenced by ongoing chemotherapy and disease progression. The analgesic effect was less pronounced but still observable in the subgroup with symptoms of depression. Conclusions: Adjunctive psychobiotic therapy appears to beneficially modulate pain perception in gastrointestinal oncology patients receiving chemotherapy, with the most pronounced effects being in non-depressed individuals. These findings suggest psychobiotics as a promising non-opioid add-on for comprehensive cancer pain management and support further investigation in larger pain-targeted trials.

Background: There is increasing interest in cosmeceuticals—cosmetic regimes incorporating a specific probiotic or postbiotic strain, fully characterized genetically and phenotypically—which, when topically applied, have the ability to modulate the skin microbiome, exhibit anti-inflammatory properties and improve the overall skin appearance by reducing signs of aging. In addition, claims have been made that emotional and psychological well-being can be improved by neuroactive substances released by the probiotics in cosmeceuticals, acting via the skin–brain axis. However, claims are somewhat generalized and imprecise, and we deemed it important to look more precisely at published research relating to cosmeceuticals. There have been very few research publications on these products, identified as neurocosmetics, and they immediately provoked strong reactions from dermatologists and psychiatrists, mainly with regard to the ethical and safety aspects of their use. Objectives/Method: The present strain-centered literature evaluation aimed to select from peer-reviewed publications referring to cosmeceuticals only those dealing with fully characterized, specific probiotic strains with documented beneficial skin properties. Eligible strains found were subsequently subjected to a secondary search to ascertain whether they also demonstrated clinical, or even experimental, evidence of strain-specific psychobiotic properties. Results: From 33 strain-specific cosmeceuticals identified, only three strains—Lactococcus lactis subsp. cremoris H61, Limosilactobacillus reuteri DSM 17938, and Weizmannia coagulans MTCC 5856—demonstrated reproducible evidence of psychobiotic potential. Conclusions: Current evidence does not support the notion that cosmeceuticals are likely to directly modulate emotional states through topical application, since the coexistence of cosmeceutical and psychobiotic properties within the same probiotic strain seems to be both uncommon and highly strain-specific and therefore of little practical, generalized use.