Skin Gas-Based Two-Dimensional Framework for Assessing Stress-Related Symptom in Humans

Stress is an important factor affecting human health and work performance, but non-invasive approaches for evaluating individual stress-related states remain limited. Human skin gases may provide physiological information related to stress and thermoregulation. In this study, we examined a skin gas-based framework for visualizing stress-related subjective states upon awakening. A total of 441 valid datasets were obtained from 100 participants. Subjective symptoms were assessed using the “Jikaku-sho Shirabe” questionnaire, which is widely used in Japan. Dermal emission fluxes of five skin gases (acetone, acetaldehyde, acetic acid, propionic acid, and hexanoic acid) were measured and converted into metabolic and vasomotor indices. Among the five questionnaire categories, the “Blurriness” score was significantly correlated with the metabolic activity index (r = 0.11, p < 0.05) and the vasomotor index (r = −0.17, p < 0.01). These indices were then plotted on a two-dimensional map, with the corresponding “Blurriness” scores assigned to each observation. The “Blurriness” scores were relatively low in the lower-right region and tended to increase toward the upper-left region, consistent with our previous pilot study. Seven-day measurements in six participants revealed individual differences in trajectories and cumulative movement across the map. These findings suggest that the proposed two-dimensional framework may provide a non-invasive approach for visualizing individual stress-related subjective states and their temporal changes. Further validation using objective measures and the development of sensors for rapid skin gas measurements may facilitate the practical application of this approach.