DISCUSSION
redness, dry, fatigue
SKIN, SKIN REDNESS
In Korea, which has four distinct seasons, many people complain of dry skin due to office heaters every winter. Therefore, we aimed to investigate the effect of indoor environmental exposure on the skin using a noninvasive method and to determine whether these changes could be improved by applying a ceramide‐containing cream.The skin temperature appeared to be affected by an increase in the ambient temperature owing to the use of heaters. The body maintains a constant skin temperature to regulate its internal environment, which is essential for homeostasis. Skin temperature also exhibits a high correlation with the temperature of the surrounding environment.Skin redness also appears to be affected by changes in skin temperature. Several studies have shown that skin temperature and redness are positively correlated, as capillaries and blood flow change with ambient temperature.Hydration and TEWL in the face did not change significantly with exposure time. This suggests that the participant had a normal healthy skin barrier and adequate sebum secretion, which helped to maintain normal levels of skin hydration and TEWL on the face. However, hydration and TEWL in the forearm showed the opposite results. After 6 h of exposure, hydration decreased rapidly and TEWL significantly increased. This is because this area is less affected by the secretion of sebum and sweat.In many studies, the skin barrier has been improved by the application of products that contain ceramide to dry skin; however, there are few studies that show its effect on healthy normal skin.One hour after cream application, the sebum content of the skin increased significantly because of the lipid components present in the cream. However, there was no significant difference in sebum content between the cream‐treated and nontreated sites after 6 h. This is because even the nontreated site can protect the skin barrier during daytime by secreting sebum with a content similar to that of the treated site. According to Boer et al.,An increase in skin temperature can cause the pores to expand and expose the skin to dry air, especially in an enclosed environment, making the skin rough and prone to wrinkles. This can lead to skin fatigue and eventually decreased skin elasticity.Hydration and elasticity were positively correlated at the treated site, while TEWL was positively correlated with pores and roughness at the nontreated site. The healthy skin of the participants maintained its barrier function through appropriate sebum secretion; however, this could still affect various aging‐related parameters. Creams containing ceramide were found to improve the elasticity, porosity, roughness, and wrinkling of the skin.Therefore, in this study, continuous exposure to indoor environments in Korea during winter was observed to cause aging. It is suggested that this problem can be prevented by applying a ceramide cream, which improves the skin barrier.