Effect of exposure of human skin to a dry environment.

Abstract

Changes in the skin conditions after exposure to low humidity have been generally experienced in everyday life, but there have been few reports to approach it-especially in healthy skin. We have examined the effect of low humidity on healthy human skin by using noninvasive measurement devices. Skin conditions on the ventral forearm and the cheek before and after 3 or 6 h exposure to low humidity were evaluated by measuring skin surface conductance, skin surface capacitance and transepidermal water loss. Skin surface replicas were also taken before and after exposure and analysed for roughness parameters--Ra (arithmetic mean roughness value), Rz (10-point height), Sm (mean value of the profile element) and VC1 (anisotropy of skin furrows). There was a significant decrease of water content of stratum corneum at both test sites from the time points 0 h to 3 h and 6 h (P < 0.01) and transepidermal water loss from the time point 0 h to 6 h (P < 0.05). Regarding the roughness parameters, a significant increase of Rz in the directions of 45 degrees/225 degrees and 90 degrees/270 degrees to the body axis and Sm in the directions of 0 degrees/180 degrees (P < 0.05) on the forearm and VC1 (P < 0.05) on the cheek. The parameter Rz also showed a tendency to increase in the directions of 45 degrees/225 degrees (P = 0.06) on the cheek. A specific pattern of the changes to be related to the Langer's lines in the surface morphology was observed. The changes of skin surface pattern in our experiment lead us to consider that exposure to low humidity even in such a short period would be related to inducing aggravation of skin texture and the formation of fine wrinkles. A short exposure of skin to a low-humidity environment induced changes in the moisture contents in the stratum corneum and skin surface pattern, which lead us to assume that a dry environment in our daily life would make fine wrinkles related to lack of water in the stratum corneum.