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Carvacrol, a natural transient receptor potential vanilloid-3 activator, has been reported to cause pruritus in mice. This study aimed to evaluate the effects of carvacrol and various antipruritic agents in humans. A stimulation test with carvacrol, β-alanine, and histamine was performed. After application of the pruritic solutions, the skin was stimulated with pinpricks. In inhibition test A, Forsythia suspensa extract, containing forsythoside B (a transient receptor potential vanilloid-3 inhibitor), was applied by pricking prior to stimulation with pruritogens. In inhibition test B, olopatadine solution, tacrolimus ointment, and Scutellaria baicalensis root extract were applied, and carvacrol was applied to the same region. Carvacrol induces moderate pruritus in humans. The pruritus was relieved by Forsythia suspensa extract and olopatadine solution after 20 min of application and by tacrolimus ointment and Scutellaria baicalenis extract after 24 h of application. These results suggest that carvacrol is a pruritogen in humans, and that carvacrol-induced pruritus is inhibited by various antipruritic agents.

Pruritus is a relatively common symptom that anyone can experience at any point in their life and is more common in the elderly. Pruritus in elderly can be defined as chronic pruritus in a person over 65 years old. The pathophysiology of pruritus in elderly is still unclear, and the quality of life is reduced. Generally, itch can be clinically classified into six types: Itch caused by systemic diseases, itch caused by skin diseases, neuropathic pruritus, psychogenic pruritus, pruritus with multiple factors, and from unknown causes. Senile pruritus can be defined as a chronic pruritus of unknown origin in elderly people. Various neuronal mediators, signaling mechanisms at neuronal terminals, central and peripheral neurotransmission pathways, and neuronal sensitizations are included in the processes causing itch. A variety of therapies are used and several novel drugs are being developed to relieve itch, including systemic and topical treatments.

Post-burn pruritus is the pruritus that occurs after burn during the rehabilitation and healing process of burn wounds. The post-burn pruritus is a common and serious complication of burn injury, which severely lowers the quality of life of the patient. Many potential treatments are available for pruritus but there is no consensus of the best single treatment yet. The precise mechanism of post-burn pruritus has not been elucidated, but it appears to have pruritogenic and neuropathic aspects. Clinically, post-burn pruritus tends to be intractable to conventional treatment but rather responds to neuroleptic agents, such as gabapentin and pregabalin. During wound healing, various neuropeptides secreted from the nerves of the skin control epidermal and vascular proliferation and connective tissue cells. When keratinocytes are activated by an itch-inducing substance, they secrete a variety of inflammatory substances that increase the susceptibility of the itch receptor. There are two mechanisms underlying post-burn neuropathic pruritus. The first one is peripheral sensitization. The second one is the intact nociceptor hypothesis. An effective treatment for post-burn pruritus will also be effective in other neuropathic and intractable itching. In this review, we summarized the interaction and mechanism of keratinocytes, immune cells, and nerve fibers related to post-burn pruritus.

Post-burn pruritus is a common and distressing sequela of burn scars. Empirical antipruritic treatments usually fail to have a satisfactory outcome because of their limited selectivity and possible side effects. Therefore, novel drug targets need to be identified. Here, we aimed to investigate the possible role of protease-activated receptor 2 (PAR2) and transient receptor potential vanniloid 3 (TRPV3), along with the relation of TRPV3 to thymic stromal lymphopoietin (TSLP). Specimens from normal (unscarred) or burn-scarred (with or without pruritus) tissue were obtained from burn patients for this study. In each sample, the keratinocytes were isolated and cultured, and the intracellular Ca 2+ level at the time of stimulation of each factor was quantified and the interaction was screened. PAR2 function was reduced by antagonism of TRPV3. Inhibiting protein kinase A (PKA) and protein kinase C (PKC) reduced TRPV3 function. TSLP mRNA and protein, and TSLPR protein expressions, increased in scars with post-burn pruritus, compared to scars without it or to normal tissues. In addition, TRPV1 or TRPV3 activation induced increased TSLP expression. Conclusively, TRPV3 may contribute to pruritus in burn scars through TSLP, and can be considered a potential therapeutic target for post-burn pruritus., Competing Interests: The authors declare no conflicts of interest.

Asivatrep is a potent and selective antagonist of transient receptor potential vanilloid subfamily V member 1 (TRPV1), which plays an important role in itch and inflammation in atopic dermatitis (AD). This current study aimed to evaluate the efficacy and safety of asivatrep cream in patients with AD. For this phase 3 double-blind, vehicle-controlled study, patients aged ≥12 years with mild to moderate AD were enrolled and randomly assigned 2:1 to the 1.0% asivatrep or vehicle group for 8 weeks of twice-daily application (n = 240). The primary end point was the proportion of patients with an Investigator's Global Assessment score (IGA) of 0 or 1 at week 8. Standard safety assessments were conducted. At week 8, significantly more patients in the asivatrep group (36.0%) than in the vehicle group (12.8%) had IGA scores of 0 or 1 (P <.001); significantly more had ≥2 points of improvement on the IGA from baseline score (20.3% vs 7.7%; P =.01). The mean percentage reduction in the Eczema Area and Severity Index (EASI) score was 44.3% for the asivatrep group and 21.4% for the vehicle group at week 8 (P <.001). Significantly more asivatrep-treated patients experienced an improvement of at least 50%, 75%, and 90% on the EASI than the vehicle group. The mean ± SD change in the pruritus visual analog scale score at week 8 was −2.3 ± 2.4 for the asivatrep group and −1.5 ± 2.4 for the vehicle group (P =.02). No significant safety issues were reported. Asivatrep improved clinical signs and symptoms of AD and was well tolerated. [Display omitted] [ABSTRACT FROM AUTHOR]

Itching is prevalent in children with skin disorders and associated with effects on their mood, quality of life, and social functioning. Surprisingly, there are no data on childhood prevalence of pruritus in the general population. The aim of this article is to explore the epidemiology, clinical manifestation, and treatment for itch (pruritus) in the pediatric population (from infancy to adolescence), and to be helpful to primary care physicians who assess and diagnose pediatric patients with itching. In this study, we searched for specific keywords using PubMed and MEDLINE (Ovid) and, then, refined the retrieved searches for each cause and treatment. As a result of reviewing the literature, atopic dermatitis was shown to be the most common cause of itching, especially during infancy and through preschool. Not only skin disorders but also systemic diseases, drugs, and postburn states can predispose an individual to itching in childhood. There are traditional and newly developed treatment modalities for itching in pediatric patients. However, because the pharmacokinetics and pharmacodynamics of childhood are different from those of adults, the medications for itching have to be applied carefully for these age groups. There are many areas to be elucidated regarding the prevalence and objective assessment of pruritus in pediatric patients. Moreover, the safety profiles of medications in the pediatric population need to be better understood. Further studies to investigate itching in childhood are warranted. [ABSTRACT FROM AUTHOR]