Effective treatment for sensitive skin: 4-t-butylcyclohexanol and licochalcone A

Integrative Approaches to Sleep Management in Skin Disease: Systematic Review

BACKGROUND

Dermatological conditions, especially when severe, can lead to sleep disturbances that affect a patient's quality of life. However, limited research exists on the efficacy of treatments for improving sleep parameters in skin conditions.

OBJECTIVE

The objective was to perform a systematic review of the literature on dermatological conditions and the treatments available for improving sleep parameters.

METHODS

A literature review was performed using the PubMed, Ovid MEDLINE, Embase, Cochrane, and ClinicalTrials.gov databases from 1945 to 2021. After filtering based on our exclusion criteria, studies were graded using the SORT (Strength of Recommendation Taxonomy) algorithm, and only those receiving a grade of "2" or better were included.

RESULTS

In total, 25 treatment studies (n=11,025) assessing sleep parameters related to dermatological conditions were found. Dupilumab appeared to be the best-supported and most effective treatment for improving sleep in atopic dermatitis (AD) but had frequent adverse effects. Topical treatments for AD were mostly ineffective, but procedural treatments showed some promise. Treatments for other conditions appeared efficacious.

CONCLUSIONS

The evaluation of sleep parameter changes in dermatological treatments is predominantly restricted to AD. Systemic interventions such as dupilumab and procedural interventions were the most efficacious. Sleep changes in other dermatoses were limited by a paucity of available studies. The inclusion of a sleep assessment component to a broader range of dermatological treatment studies is warranted.

Dipeptide-1 modified nanostructured lipid carrier-based hydrogel with enhanced skin retention and topical efficacy of curcumin

Topical administration of curcumin (CUR), a natural polyphenol with potent anti-inflammation and analgesic activities, provides a potential approach for local skin diseases. However, the drug delivery efficiency is highly limited by skin barriers and poor bioavailability of CUR. Herein, we propose hydrogel containing CUR-encapsulated dipeptide-1-modified nanostructured lipid carriers (CUR-DP-NLCs gel) to enhance topical drug delivery, and improve the topical therapeutic effect. The prepared CUR-DP-NLCs were characterized and were suitably dispersed into the Pluronic F127 hydrogel for topical application. The optimized CUR-DP-NLCs had a particle size of 152.6 ± 3.47 nm, a zeta potential of -33.1 ± 1.46 mV, an entrapment efficiency of 99.83 ± 0.14%, and a spherical morphology. X-ray diffraction (XRD) studies confirmed that CUR was successfully entrapped by the NLCs in an amorphous form. CUR-DP-NLCs gel exhibited sustained release over 48 h and significantly increased the skin retention of CUR. In vitro skin retention of CUR with CUR-DP-NLCs gel was 2.14 and 2.85 times higher than that of unmodified NLCs gel and free CUR, respectively. Fluorescence microscopy imaging revealed the formed nanoparticles accumulated in the hair follicles with prolonged retention time to form a drug reservoir. The hematoxylin-eosin staining showed that CUR-DP-NLCs gel could change the microstructure of skin layers and disturb the skin barriers. After topical administration to mice, CUR-DP-NLCs gel showed better analgesic and anti-inflammatory activities with no potentially hazardous skin irritation. These results concluded that CUR-DP-NLCs gel is a promising strategy to increase topical drug delivery of CUR in the treatment of local skin diseases.

Clinical study of a spray containing birch juice for repairing sensitive skin

Sensitive skin is described as an unpleasant sensory response to a stimulus that should not cause a sensation. Sensitive skin affects an increasing proportion of the population. Sixty-seven participants who tested positive to lactic acid sting test were recruited and randomized into two groups to observe the clinical efficacy and safety of a new birch juice spray for repairing sensitive skin. One group used test spray A, while the other group used spray B as a control. Both groups were sprayed six times daily for 28 days. Noninvasive testing instruments were used to measure stratum corneum hydration, sebum content, transepidermal water loss rates, skin blood perfusion and current perception threshold before and after using spray. Facial images were captured by VISIA-CR, and the image analysis program (Image-Pro Plus) was used to analyze these to obtain the redness value of the facial skin. Moreover, lactic acid sting test scores and participants' self-assessments were also performed at baseline, week 2 and week 4. Both sprays A and B significantly decreased the lactic acid sting test score, transepidermal water loss rates, skin blood perfusion, and redness, while increasing the stratum corneum hydration. Compared to spray B, spray A increased sensory nerve thresholds at 5 Hz and decreased the transepidermal water loss rates, skin blood perfusion, and lactic acid sting test score. Sprays containing birch juice improved cutaneous biophysical properties in participants with sensitive skin.

Functional validation of co-culture model of human keratinocytes and neuronal cell line for sensitive skin by using transient receptor potential channel vanilloid subfamily member 1 antagonist

BACKGROUND

Sensitive skin is a subjective cutaneous hyper-reactivity that occurs in response to various innocuous stimuli. Keratinocytes have recently been shown to participate in sensory transduction by releasing many neuroactive molecules that bind to intra-epidermal free nerve endings and modulate nociception. In the literature, the characterization of these interactions has been based on the co-culture of keratinocyte and mammalian-origin neuronal cell lines. In this study, we established an in vitro model based on a co-culture of primary human keratinocytes and differentiated SH-SY5Y cells, a human neuronal cell line.

METHODS

Human epidermal keratinocytes and SH-SY5Y cells were monocultured and co-cultured. Changes in calcium influx, substance P, inflammatory cytokines, and neuropeptides between the monoculture and co-culture groups treated with capsaicin only and capsaicin with transient receptor potential channel vanilloid subfamily member 1 (TRPV1) antagonist, trans-4-tert-butylcyclohexanol (TTBC), together. In addition, the difference in stinging sensation was evaluated by applying it to the volunteers.

RESULTS

When SH-SY5Y cells were co-cultured with keratinocytes, they had no significant effect on axonal development. Substance P was also released after capsaicin treatment and reduced by TTBC under co-culture conditions. Moreover, the expression of inflammatory cytokines and neuropeptides was significantly increased in co-cultured keratinocytes compared to that under monoculture conditions. In addition, the stinging sensation was significantly induced after the application of capsaicin in vivo and was relieved after the application of the TRPV1 antagonist.

CONCLUSION

We demonstrated that the novel co-culture model is functionally valid through capsaicin and TRPV1 antagonist. We also confirmed that TTBC could be used for the treatment of sensitive skin through a co-culture model and in vivo tests. This co-culture model of keratinocytes and SH-SY5Y cells may be useful in vitro alternatives for studying the close communication between keratinocytes and neuronal cells and for screening therapeutic drugs for sensitive skin.

Inhibition of Nematocyst Discharge from Pelagia noctiluca (Cnidaria: Scyphozoa)—Prevention Measures against Jellyfish Stings

Pelagia noctiluca stings are common in Mediterranean coastal areas and, although the venom is non-lethal, they are painful. Due to its high toxicity and abundance, P. noctiluca is considered a target species for the focus of research on active ingredients to reduce the symptoms of its sting. To determine the effect of 31 substances and formulations on nematocyst discharge, we performed three tests: (1) screening of per se discharge activator solutions, (2) inhibitory test with nematocyst chemical stimulation (5% acetic acid) and (3) inhibitory test quantifying the hemolytic area. Ammonia, barium chloride, bleach, scented ammonia, carbonated cola, lemon juice, sodium chloride and papain triggered nematocyst discharge. All of them were ruled out as potential inhibitors. Butylene glycol showed a reduction in nematocyst discharge, while the formulations of 10% lidocaine in ethanol, 1.5% hydroxyacetophenone in distilled water + butylene glycol, and 3% Symsitive® in butylene glycol inhibited nematocyst discharge. These last results were subsequently correlated with a significant decrease in hemolytic area in the venom assays versus seawater, a neutral solution. The presented data represent a first step in research to develop preventive products for jellyfish stings while at the same time attempting to clarify some uncertainties about the role of various topical solutions in P. noctiluca first-aid protocols.

Prenylated Flavonoids in Topical Infections and Wound Healing

The review presents prenylated flavonoids as potential therapeutic agents for the treatment of topical skin infections and wounds, as they can restore the balance in the wound microenvironment. A thorough two-stage search of scientific papers published between 2000 and 2022 was conducted, with independent assessment of results by two reviewers. The main criteria were an MIC (minimum inhibitory concentration) of up to 32 µg/mL, a microdilution/macrodilution broth method according to CLSI (Clinical and Laboratory Standards Institute) or EUCAST (European Committee on Antimicrobial Susceptibility Testing), pathogens responsible for skin infections, and additional antioxidant, anti-inflammatory, and low cytotoxic effects. A total of 127 structurally diverse flavonoids showed promising antimicrobial activity against pathogens affecting wound healing, predominantly Staphylococcus aureus strains, but only artocarpin, diplacone, isobavachalcone, licochalcone A, sophoraflavanone G, and xanthohumol showed multiple activity, including antimicrobial, antioxidant, and anti-inflammatory along with low cytotoxicity important for wound healing. Although prenylated flavonoids appear to be promising in wound therapy of humans, and also animals, their activity was measured only in vitro and in vivo. Future studies are, therefore, needed to establish rational dosing according to MIC and MBC (minimum bactericidal concentration) values, test potential toxicity to human cells, measure healing kinetics, and consider formulation in smart drug release systems and/or delivery technologies to increase their bioavailability.

Role of Licochalcone A in Potential Pharmacological Therapy: A Review

Licochalcone A (LA), a useful and valuable flavonoid, is isolated from Glycyrrhiza uralensis Fisch. ex DC. and widely used clinically in traditional Chinese medicine. We systematically updated the latest information on the pharmacology of LA over the past decade from several authoritative internet databases, including Web of Science, Elsevier, Europe PMC, Wiley Online Library, and PubMed. A combination of keywords containing “Licochalcone A,” “Flavonoid,” and “Pharmacological Therapy” was used to help ensure a comprehensive review. Collected information demonstrates a wide range of pharmacological properties for LA, including anticancer, anti-inflammatory, antioxidant, antibacterial, anti-parasitic, bone protection, blood glucose and lipid regulation, neuroprotection, and skin protection. LA activity is mediated through several signaling pathways, such as PI3K/Akt/mTOR, P53, NF-κB, and P38. Caspase-3 apoptosis, MAPK inflammatory, and Nrf2 oxidative stress signaling pathways are also involved with multiple therapeutic targets, such as TNF-α, VEGF, Fas, FasL, PI3K, AKT, and caspases. Recent studies mainly focus on the anticancer properties of LA, which suggests that the pharmacology of other aspects of LA will need additional study. At the end of this review, current challenges and future research directions on LA are discussed. This review is divided into three parts based on the pharmacological effects of LA for the convenience of readers. We anticipate that this review will inspire further research.

New Highly Potent NLRP3 Inhibitors: Furanochalcone Velutone F Analogues

The NLRP3 inflammasome has now emerged as one of the most appealing drug targets for many inflammation-related diseases. Velutone F, a natural NLPR3 inhibitor, identified in our previous study has been limited in application by its low in planta abundance, weak activity, and complicated synthetic routes. To address these needs, structural optimization of velutone F led to a series of novel NLRP3 inhibitors. Among them, compound 14c exerted remarkable inhibitory activity with an IC₅₀ value in the nanomolar range (251.1 nM) and was approximately 5-fold more potent than velutone F. Moreover, the synthesis method of 14c was simple, easy to handle, and scalable. Compound 14c could suppress NLRP3 inflammasome activation by attenuating ASC speck formation. Most importantly, compound 14c reduced peritoneal neutrophil influx in mice and IL-1β in the spleen in the MSU-induced peritonitis in LPS-primed mouse model. Taken together, compound 14c is a prospective lead compound in the discovery of NLRP3 inflammasome inhibitors.

In vitro characterization and clinical evaluation of skin hydration by two formulations mimicking the skin's natural components

BACKGROUND

We have developed innovative base formulations that were designed to mimic the skin with respect to its components and galenic structure. Components include water, proteins, lipids, sugars and minerals.

OBJECTIVES

We characterized formulations and their skin penetration using in vitro methods and evaluated their impact on skin hydration in a clinical trial.

METHODS

Scanning electron microscopy (SEM) imaging and X-ray diffraction were used to analyse formulations as well as formulation impact on the stratum corneum (SC) structure. Mass spectrometry imaging (MSI) was used to compare formulation ingredients with SC components and to detect their distribution in the skin. Clinical studies were performed to confirm effects on skin hydration and investigate potential adverse skin effects (irritation and sensitization).

RESULTS

SEM and X-ray diffraction of the formulations showed that lipids were organized in sheets similar to SC lipids. MSI demonstrated similarities between formulation components and skin constituents, as well as a good penetration into the skin. The formulations did not modify the lamellar organization of the SC lipids, but they increased the relative proportion of the crystallized lipids and some of the amorphous lipids. In in vivo studies, a high level of hydration was maintained over 24 h after application with an intense and 'very good hydration'. Both formulations were shown to be non-(photo)sensitizers with excellent tolerance. Sensorial evaluation indicated the formulations were not oily or sticky and maintained the skin's suppleness over time. Formulations had a 'nude skin' touch and created a natural protective film.

CONCLUSIONS

The two formulations were well-tolerated and increased skin hydration in clinical subjects, an effect that could contribute to the alleviation of sensitive skin. The formulations were shown to resemble the lipid organization of the stratum corneum, as well as penetrate the skin without disrupting the lipid lamella organization.

Pharmacological Effects and Underlying Mechanisms of Licorice-Derived Flavonoids

Glycyrrhizae Radix et Rhizoma is the most frequently prescribed natural medicine in China and has been used for more than 2,000 years. The flavonoids of licorice have garnered considerable attention in recent decades due to their structural diversity and myriad pharmacological effects, especially as novel therapeutic agents against inflammation and cancer. Although many articles have been published to summarize different pharmacological activities of licorice in recent years, the systematic summary for flavonoid components is not comprehensive. Therefore, in this review, we summarized the pharmacological and mechanistic data from recent researches on licorice flavonoids and their bioactive components.

Sensitive skin: Active ingredients on the spotlight

OBJECTIVE

Sensitive skin is characterized by self-reported sensory perceptions in response to stimuli that should not provoke unpleasant sensations. Cosmetic products for sensitive skin are designed to minimize these symptoms. This study aimed to unveil the most used active ingredients for sensitive skin in facial care products from the pharmacy and parapharmacy channel.

METHODS

A pool of products from the pharmacy and parapharmacy channel whose label included the expressions 'sensitive skin', 'reactive skin' or 'intolerant skin' were analysed. The active ingredients were identified from product compositions and ranked in descending order of occurrence. The scientific evidence regarding the mechanism of action and efficacy of each ingredient was also compiled.

RESULTS

Eighty-eight products from 19 multinational brands were included. Niacinamide leads the top, followed by Avena sativa, allantoin, glycyrrhetinic acid and derivatives and Laminaria ochroleuca. Ingredients that can reduce skin inflammation and act on the skin barrier were used in more than half of the products analysed. The clinical studies regarding the active ingredients used in these products remain sparse and lack methodological quality. Among the top ingredients, niacinamide, panthenol and acetyl dipeptide-1 cetyl ester were the only ones studied on volunteers having sensitive skin, while acetyl dipeptide-1 cetyl ester and palmitoyl tripeptide-8 were designed to act on the molecular targets involved in this condition.

CONCLUSION

This study reveals the most used active ingredients in cosmetic products for sensitive skin, as well as the scientific evidence supporting their efficacy and the mechanisms of action. This insight is meaningful for dermatologists and other health professionals to provide customized advice based on the symptomatology of individuals with sensitive skin, and for the formulation of cosmetic products and design of new active ingredients.

Usage of Synthetic Peptides in Cosmetics for Sensitive Skin

Sensitive skin is characterized by symptoms of discomfort when exposed to environmental factors. Peptides are used in cosmetics for sensitive skin and stand out as active ingredients for their ability to interact with skin cells by multiple mechanisms, high potency at low dosage and the ability to penetrate the stratum corneum. This study aimed to analyze the composition of 88 facial cosmetics for sensitive skin from multinational brands regarding usage of peptides, reviewing their synthetic pathways and the scientific evidence that supports their efficacy. Peptides were found in 17% of the products analyzed, namely: acetyl dipeptide-1 cetyl ester, palmitoyl tripeptide-8, acetyl tetrapeptide-15, palmitoyl tripeptide-5, acetyl hexapeptide-49, palmitoyl tetrapeptide-7 and palmitoyl oligopeptide. Three out of seven peptides have a neurotransmitter-inhibiting mechanism of action, while another three are signal peptides. Only five peptides present evidence supporting their use in sensitive skin, with only one clinical study including volunteers having this condition. Noteworthy, the available data is mostly found in patents and supplier brochures, and not in randomized placebo-controlled studies. Peptides are useful active ingredients in cosmetics for sensitive skin. Knowing their efficacy and synthetic pathways provides meaningful insight for the development of new and more effective ingredients.

Impact of ultraviolet radiation and exposome on rosacea: Key role of photoprotection in optimizing treatment

Background

Pathophysiology of rosacea is not completely understood and involves a complex interaction among genetics, ultraviolet (UV) light, microorganisms, impaired skin barrier, neuronal and vascular dysfunction, and immune system disruption.

Aims

To describe the etiology of rosacea with an emphasis on the role of UV radiation and exposome, and to review the importance of non‐pharmacologic strategies focusing on photoprotection.

Methods

We conducted a narrative review of the literature. We performed literature searches with PubMed from January 1990 to November 2020 using the keywords “rosacea”, “pathogenesis”, “ultraviolet radiation”, “exposome”, “photoprotection”, “sunscreens” and “non‐pharmacologic agents”. The search was limited to English, Spanish, and French language articles.

Results

Several environmental factors such as UV light, diverse microorganisms, air pollution, tobacco smoking, nutrition, and psychological stress showed to trigger or worsen rosacea. UV radiation was reported to induce pro‐inflammatory, pro‐angiogenic, and pro‐fibrotic responses. We found 6 original articles about the impact of sunscreens on rosacea. The use of sunscreens containing ingredients with emollient, anti‐inflammatory, and/or vasoregulatory properties was shown to significantly improve symptomatology.

Conclusion

UV radiation and the exposome play a key role in the development of rosacea. UV light is implicated in all significant aspects of rosacea: skin inflammation, neoangiogenesis, telangiectasia, and fibrosis, and may even initiate rosacea. While the use of sunscreens is widely recommended, the literature on the impact of photoprotection in rosacea is scarce. Adequately formulated sunscreens could not only provide the required level of photoprotection, but may also help to mitigate the barrier dysfunction, neutralize facial redness (tinted sunscreens), and decrease inflammation and vascular dysfunction.

Pharmacological Properties of Chalcones: A Review of Preclinical Including Molecular Mechanisms and Clinical Evidence

Chalcones are among the leading bioactive flavonoids with a therapeutic potential implicated to an array of bioactivities investigated by a series of preclinical and clinical studies. In this article, different scientific databases were searched to retrieve studies depicting the biological activities of chalcones and their derivatives. This review comprehensively describes preclinical studies on chalcones and their derivatives describing their immense significance as antidiabetic, anticancer, anti-inflammatory, antimicrobial, antioxidant, antiparasitic, psychoactive, and neuroprotective agents. Besides, clinical trials revealed their use in the treatment of chronic venous insufficiency, skin conditions, and cancer. Bioavailability studies on chalcones and derivatives indicate possible hindrance and improvement in relation to its nutraceutical and pharmaceutical applications. Multifaceted and complex underlying mechanisms of chalcone actions demonstrated their ability to modulate a number of cancer cell lines, to inhibit a number of pathological microorganisms and parasites, and to control a number of signaling molecules and cascades related to disease modification. Clinical studies on chalcones revealed general absence of adverse effects besides reducing the clinical signs and symptoms with decent bioavailability. Further studies are needed to elucidate their structure activity, toxicity concerns, cellular basis of mode of action, and interactions with other molecules.

Cinnamtannin B1 attenuates rosacea-like signs via inhibition of pro-inflammatory cytokine production and down-regulation of the MAPK pathway

Background

Rosacea is a common inflammatory disease of facial skin. Dysregulation of innate immunity with enhanced inflammation and increased abundance of LL-37 at the epidermal site is a characteristic feature of rosacea. Cinnamtannin B1 (CB1) is a condensed tannin with anti-inflammatory and anti-microbial activities. The aims of the study were to evaluate the potential of CB1 as a therapy for rosacea and to characterize the potential mechanisms of action.

Methods

We intraperitoneally administered 20 mg/kg CB1 once daily for 2 days into the LL-37-induced mouse model of rosacea. The effects of CB1 in vivo were evaluated by the observations of lesions, histology, immunohistochemistry, and the transcription and translation of pro-inflammatory cytokines and chemokines. Human keratinocyte HaCaT and monocyte THP-1 were used to characterize the effects of CB1 on LL-37-induced inflammation in vitro. The changes in pro-inflammatory chemokine interleukin-8 (IL-8) were quantitated by enzyme-linked immunosorbent assay (ELISA), and the expressions of genes involved were determined by Western blotting.

Results

CB1 attenuated local redness, inflammation, and neutrophil recruitment in the mouse model of rosacea in vivo. CB1 suppressed myeloperoxidase (MPO) and macrophage inflammatory protein 2 (MIP-2) production, a functional homolog of interleukin-8 (IL-8), at the lesions. In vitro experiments confirmed that CB1 reversed the LL-37-induced IL-8 production in human keratinocytes HaCaT and monocyte THP-1 cells. CB1 inhibited IL-8 production through downregulating the phosphorylation of extracellular signal-regulated kinase (ERK) in the mitogen-activated protein kinase (MAPK) pathway.

Conclusion

CB1 attenuated LL-37-induced inflammation, specifically IL-8 production, through inhibiting the phosphorylation of ERK. CB1 has potential as a treatment for rosacea.

An herbal cream reduces erythema of sensitive skin

BACKGROUND

Sensitive skin manifests itself as a syndrome defined by the occurrence of unpleasant sensations such as stinging, burning, and pruritus. Though not life-threatening, it can negatively impact the quality of people's lives because of symptoms and clinical signs. Although some skin care products can alleviate symptoms of sensitive skin, a product that can improve multiple abnormalities of sensitive skin are largely unavailable.

AIMS

To assess the efficacy of a newly developed herbal cream in reducing erythema.

METHODS

A randomized double-blind and self-controlled trial was carried out on a total of 35 volunteers. The test cream (A) was applied topically to one side of the face twice-daily, while the control cream (B) was applied to the other side of the face. Parameters were evaluated prior to, 14, and 28 days after topical applications. Primary endpoints included changes in erythema area, erythema index (EI), and a* value. Transepidermal water loss rates (TEWL), stratum corneum (SC) hydration, and lactic acid sting test (LAST) score, as well as the L* value, served as secondary endpoints.

RESULT

Treatments with either cream A or B markedly reduced erythema area, EI, and a* value. Significant reductions in both TEWL and L* value were also observed following topical applications of either cream A or B. Moreover, cream A decreased LAST score. Finally, the satisfaction rate of cream A was higher than that of cream B.

CONCLUSION

The new herbal cream improves cutaneous biophysical properties in subjects with sensitive skin, especially in reducing erythema.

Clinical and in vitro evaluation of new anti-redness cosmetic products in subjects with winter xerosis and sensitive skin

Objective

To demonstrate the in vitro activities of panthenol, palmitoylethanolamide (PEA), and niacinamide (NAM) and determine the biophysical properties, clinical safety, tolerability together with efficacy of two developmental anti‐redness (AR) formulations containing these ingredients, in alleviating facial redness associated with winter xerosis in healthy volunteers with sensitive skin.

Methods

The anti‐inflammatory and skin protective properties of panthenol, PEA and NAM were evaluated in vitro. The physical properties of the AR formulations were analysed using measurement of water vapour transport rate (WVTR) and infrared spectroscopy. Clinical studies were performed between the months of December and April (2014–2015) with efficacy assessed during the winter. Facial redness, irritation, sensitization potential, photo‐irritation, and photo‐sensitization were evaluated. Self‐assessed adverse reactions were reported in diaries of use.

Results

Panthenol and PEA reduced prostaglandin E₂, interleukin‐6, and thymic stromal lymphopoietin levels in vitro, while NAM induced nicotinamide adenine dinucleotide (NAD) levels and the keratinocyte differentiation markers: filaggrin (2‐fold increase, P < 0.001), loricrin (2‐fold increase, P < 0.05), involucrin (2 fold increase, P < 0.001) & peroxisomal proliferator activated receptor‐alpha (1.5 fold increase, P < 0.05). The two AR products exhibited low WVTR vs. no treatment (P < 0.001) and displayed an ordered lipid structure. The day cream formulation protected against ultraviolet B radiation in vitro. A total of 382 participants were included in clinical studies which showed the AR formulations significantly improved facial redness associated with winter xerosis (Day 29 mean change from baseline: AR day cream 0.77 (P < 0.001); AR serum 0.67 (P < 0.001)). No irritation, sensitization, photo‐irritation, photo‐sensitization or product‐related adverse reactions were observed or reported in the clinical studies.

Conclusion

The new products significantly improved skin redness associated with winter xerosis in participants with self‐perceived sensitive skin. Both products were well tolerated with a suitable safety profile for topical use in subjects with sensitive skin.

New Herbal Biomedicines for the Topical Treatment of Dermatological Disorders

Herbal extracts and isolated plant compounds play an increasing role in the treatment of skin disorders and wounds. Several new herbal drugs, medicinal products and cosmetic products for the treatment of various skin conditions have been developed in recent years. In this nonsystematic review, we focus on herbal drugs that were tested in controlled clinical studies or in scientifically sound preclinical studies. The herbal biomedicines are intended to treat atopic dermatitis (St. John's wort, licorice, tormentil, bitter substances, evening primrose), psoriasis (araroba tree, lace flower, barberry bark, indigo, turmeric, olibanum, St. John's wort), actinic keratosis (birch bark, petty spurge), herpes simplex (lemon balm, sage and rhubarb), rosacea (green tea, licorice, tormentil) and acne vulgaris (tea tree oil, green tea, hop), or to improve photo protection (green tea, Dyer's weed, cocoa tree, carotinoids, licorice), aesthetic dermatology (licorice, pine bark, gotu kola) and wound healing (birch bark, onion).

A Review of the Pharmacological Efficacy and Safety of Licorice Root from Corroborative Clinical Trial Findings

Since ancient times, licorice, the root of Glycyrrhiza glabra, has been known to have a wide spectrum of therapeutic effects. Glycyrrhizin is cleaved to glycyrrhizic acid, which is subsequently converted to glycyrrhetic acid by human intestinal microflora. Glycyrrhetic acid is a potent inhibitor of 11β-hydroxysteroid dehydrogenase (11β-HSD) and performs a range of corticosteroid-like activities. The pharmacologic effects of licorice contribute to its anti-inflammatory, antioxidative, anti-allergenic, and antimicrobial properties. Licorice has been used to treat liver disease, gastrointestinal disorders, oral disease, and various skin disorders and has been used in gum, candy, herbs, alcoholic beverages, and food supplements. Licorice and its extracts, especially glycyrrhizin, can be taken orally, through the skin (in the form of gels and oils), and intravenously. Licorice demonstrates mineralocorticoid-like activity not only by inhibiting 11β-HSD2, but also by binding to a mineralocorticoid receptor, leading to potentially adverse risks of mineralocorticoid-like overactivity. Chronic use of licorice can lead to hypokalemia and hypertension, and some people are more sensitive to licorice exposure. Based on clinical trials, this review summarizes the positive effects of licorice and other reported side effects.

Role of Keratinocytes in Sensitive Skin

Sensitive skin is a clinical syndrome defined by the occurrence of unpleasant sensations such as burning, stinging, tingling, pricking, or itching in response to various normally innocuous physical, chemical, and thermal stimuli. These particular symptoms have led the consideration of a potential dysfunction of the intra-epidermal nerve fibers (IENF) that are responsible for pain, temperature, and itch perception. This neuronal hypothesis has just been reinforced by recent studies suggesting that sensitive skin could become assimilated to small fiber neuropathy. Meanwhile, the involvement of keratinocytes, the pre-dominant epidermal cell type, has so far mainly been considered because of their role in the epidermal barrier. However, keratinocytes also express diverse sensory receptors present on sensory neurons, such as receptors of the transient receptor potential (TRP) family, including Transient Receptor Potential Vallinoid 1 (TRPV1), one of the main transducers of painful heat which is also involved in itch transduction, and Transient Receptor Potential Vallinoid 4 (TRPV4) which is depicted as a heat sensor. While TRPV1 and TRPV4 are expressed both by sensory neurons and keratinocytes, it has recently been demonstrated that the specific and selective activation of TRPV1 on keratinocytes is sufficient to induce pain. Similarly, the targeted activation of keratinocyte-expressed TRPV4 elicits itch and the resulting scratching behavior. So, contrary to classical conception, the IENF are not the exclusive transducers of pain and itch. In light of these recent advances, this review proposes to consider the putative role of epidermal keratinocytes in the generation of the unpleasant sensations characteristic of sensitive skin syndrome.

The Prevalence of Sensitive Skin

Sensitive skin has been described as unpleasant sensory responses to stimuli that should not provoke such sensations. Objectively measurable signs of irritation are not always present in individuals with sensitive skin, however, subjective sensory effects such as, itching, burning, stinging, tightness, and dryness, are consistently present. Given the subjective nature of the phenomenon known as sensitive skin, surveys have been a popular approach to evaluating the prevalence of this condition among the general population, and a number of them have been conducted worldwide. Overall, ~60–70% of women and 50–60% of men report having some degree of sensitive skin. However, there are differences between populations in various geographies, and perceptions of sensitive skin at specific anatomic sites. This article is a review of survey data on the prevalence of self-declared sensitive skin in various geographies, among different gender and age groups, and at various anatomic sites. In addition, we review the factors that may contribute to sensitive skin, and the physiological characteristics associated with this condition, including impaired barrier function and heightened neural reactions.

Randomized investigator-blinded comparative study of moisturizer containing 4-t-butylcyclohexanol and licochalcone A versus 0.02% triamcinolone acetonide cream in facial dermatitis

BACKGROUND

Facial dermatitis can result from various conditions, some of which are of a chronic and relapsing nature. The use of topical corticosteroid therapy may lead to additional adverse effects.

OBJECTIVE

To compare the efficacy of moisturizer containing 4-t-butylcyclohexanol, which acts as a sensitivity regulator, and licochalcone A, an anti-inflammatory agent from the licorice plant Glycyrrhiza inflata, with that of 0.02% triamcinolone acetonide (TA) for the treatment of facial dermatitis.

METHODS

This was a randomized, prospective, investigator-blinded study. Eighty participants with mild to moderate facial dermatitis were randomly treated with either the test facial moisturizer or 0.02% TA twice daily for the first 2 weeks. For the subsequent 2 weeks, all patients used only the test moisturizer. Clinical assessment by investigators, bioengineering measurements, patients' subjective evaluation, and clinical photography were performed at baseline, week 2, and week 4.

RESULTS

Both treatments showed a statistically significant improvement with regard to physician clinical assessment, skin hydration, transepidermal water loss, and patient-assessed visual analog scale after 2 and 4 weeks of treatment compared with baseline. The test facial moisturizer produced better skin hydration than TCS. The improvement in TEWL after 4 weeks of using the test moisturizer was comparable with 2-week treatment with 0.02% TA cream. However, subjective evaluation by patients indicated that TA more rapidly improved sensation sensitivity.

CONCLUSION

The test facial moisturizer was slower than 0.02% TA in improving facial dermatitis, but showed greater benefit in erythema control and skin hydration.

Grifolin derivatives from Albatrellus ovinus as TRPV1 receptor blockers for cosmetic applications

OBJECTIVE

Blocking the TRPV1 receptor is an interesting approach for the treatment of sensitive skin. Here we investigated the potential of grifolin derivatives from Albatrellus ovinus to act as TRPV1 receptor blockers and their potential to serve as cosmetic active ingredients.

METHODS

Binding characteristics of grifolin derivatives from Albatrellus ovinus were determined in competitive and functional in vitro assays to achieve IC₅₀ values. The TRPV1 receptor was activated in vivo with capsaicin and noxious heat to investigate skin reddening, microcirculation, skin sensations and heat pain thresholds.

RESULTS

Grifolin derivatives extracted from Albatrellus ovinus proved to inhibit the TRPV1 receptor in vitro and in vivo. Besides suppression of the TRPV1 receptor activity upon chemical stimulation with capsaicin, thermal activation was shown to be inhibited as well by application of cosmetic formulations containing 3% Albatrellus ovinus extract. The reduction of stinging and burning sensations as well as reduction of reddening and microcirculation upon irritation with capsaicin or thermal stress proved efficacy in vivo.

CONCLUSION

Grifolin derivatives from Albatrellus ovinus are able to serve as fungal-derived TRPV1 receptor blockers with capability to serve as a cosmetic active ingredient on sensitive skin.