Thermal Imaging and Infrared Thermometry to Assess Post-wash Cooling: Method Development and Standardization.

The cooling sensation imparted by topical rinse-off formulations, such as facial cleansers, represents a critical sensorial attribute influencing consumer perception and product acceptability. Despite its subjective nature, this effect can be objectively quantified using non-invasive tools such as infrared (IR) thermography and non-contact infrared thermometry. The aim was to develop and internally standardize a reproducible methodology for assessing the immediate cooling effect of rinse-off facial products using IR thermal imaging and non-contact infrared temperature measurement. An exploratory, non-randomized, open-label, crossover evaluation was conducted on 20 healthy male volunteers (aged 22-40 years). Each participant underwent facial skin temperature assessments at three predefined time points: baseline (resting state), post-exercise (to elevate skin temperature physiologically), and immediately after facial cleansing. The test arm involved application of a commercial rinse-off face wash, while the control arm followed cleansing with water only. Facial skin surface temperature was recorded using both a high-resolution IR thermographic camera and a point-based non-contact infrared thermometer. A statistically significant reduction in mean facial skin temperature was observed post-exercise in both the test and control arms, suggesting localized evaporative cooling. Following product application, the test arm demonstrated a more pronounced decrease in temperature compared to the control. Notably, IR thermography captured broader, region-specific thermal variations and greater magnitude of change than non-contact thermometry, which registered only minor point-specific differences. The findings support the feasibility and sensitivity of infrared thermography as a robust, objective technique for evaluating the immediate cooling effects of rinse-off cosmetic products. This internally standardized method may be reliably applied in future clinical research to substantiate thermoregulatory or sensorial efficacy claims associated with topical formulations. Specifically, its application may aid in the comparative assessment of novel cooling agents, guide formulation optimization, and support regulatory submissions or marketing claims related to cooling efficacy in both dermatological and cosmetic product development.