Itching Caused by TRPV3 (Transient Receptor Potential Vanilloid-3) Activator Application to Skin of Burn Patients

Background and objectives: Postburn pruritus is a common complication of scars in burn patients. In our previous study, we discovered increased expression of TRPV3, TRPV4, and TRPA1. Among them, TRPV3, in particular, is predominantly expressed in the epidermis of the tissue of pruritic burn scars. We sought to evaluate the correlation between the expression of TRPV3 activators and itching after application of TRPV3 activator carvacrol over burn scars. Materials and Methods: Design: This was a double-blind clinical trial with non-randomized distribution. Setting: This study was performed in a hospital setting. Patients or participants: Patients with itching of burn scars (numerical rating scale (NRS), n = 8; Group 1 and NRS, >= 3; n = 16, Group 2) and healthy volunteers (n = 18, Group 3) were included. Interventions: The investigational drug carvacrol (100%, 75%, and 50%) and control drug (10% ethanol) were applied over the scars using IQ Ultimate (TM) 1 x 1 cm chamber sheets. Main variables of interest: The presence of pruritus, erythema, edema, and other skin lesions was evaluated. The verbal NRS scores were also compared. Results: Carvacrol induced more itching in Group 2 than in Groups 1 and 3. In Group 2, 100%, 75%, and 50% carvacrol caused significantly more itching (NRS score, 5.18 +/- 3.04, 5.18 +/- 3.04, and 4.93 +/- 2.96, respectively) than that in Group 1 (NRS score, 1.00 +/- 1.80, 1.00 +/- 1.80, and 1.00 +/- 1.80, respectively) and Group 3 (NRS score, 2.38 +/- 1.94, 1.27 +/- 1.32, respectively). Conclusions: The TRPV3 activator carvacrol can cause itching if applied over burn scars. This study can help understand the mechanism and prognosis of post-burn itching and contribute to the development of its treatment.