This study presents a preliminary, exploratory longitudinal analysis of facial skin temperature (FST) spatial distributions using facial thermal imagery (FTI) acquired over six months from summer to winter. We aimed to quantify the typical spatial distribution of FST and assess intra- and inter-individual variability under controlled laboratory conditions. As an initial step toward defining a reference distribution, we compared FST spatial patterns measured during baseline sessions with those obtained under an experimentally induced, non-clinically validated abnormal condition. The results showed relatively small inter-individual variability in FST spatial distributions within the sampled population, suggesting a consistent pattern across participants. In contrast, the abnormal condition produced measurable deviations from the baseline pattern, particularly when distributions were expressed using Z-score normalization. Because this study did not include clinical validation, external control groups, or real-world testing, the findings should be interpreted as suggestive rather than definitive. Future work should include clinical trials and broader participant cohorts to validate the proposed reference distribution, evaluate additional confounders (e.g., circadian effects and environmental variability), and test robustness in real-world settings to support translational applications such as health monitoring. • Long-term observations in a small exploratory cohort suggest a consistent spatial pattern in facial skin temperature. • Z-score scaling was the most stable across repeated measurements and was sensitive to stress-task–related deviations in spatial distribution. • Spatial features of facial skin temperature may support non-contact monitoring; however, clinical and real-world validation is required.
Nagumo et al. (Fri,) studied this question.