Topically applied methyl nicotinate evokes a temporary inflammation on human skin

Some challengers such as methylnicotinate (MN) have been used in human models to study the anti-inflammatory effect of topical formulations. However, MN skin responses are still poorly understood and widely varied. In the present study we aim to contribute to better characterise those responses. Eight healthy participants were selected. All procedures were approved by the institutional Ethics Committee. Two aqueous MN dilutions (0.5% and 1.0%) were left in contact for 1 minute in the anterior forearm skin. Following exposure, skin reactions were clinically and biometrically assessed at 30, 60 and 120 minutes and compared with baseline. Measurements involved the ICDRG clinical score scale and select analytical technologies - laser Doppler flowmetry, Polarised Spectroscopy, Transepidermal Water Loss Meter, and High Resolution Sonography. Results have shown that MN application evoked a maximal response at 30 minutes with an increase in the ICDRG score between 1-2. Significant changes in TEWL and microcirculation were observed, as was an increased dermal hypoecogenicity (edema), detected by HRS. These effects are compatible with a localised short-duration inflammation and reinforce the interest of MN to be used as a safe and controllable challenger in human models.