Dermal fluid translocation is an important determinant of the diurnal variation in human skin thickness

Background Ultrasonography has been used as a non-invasive approach to meas ure skin thickness. To date there have been no studies on diurnal variation s in skin thickness. Objectives To evaluate diurnal variations in skin thickness and to compare these with corresponding echogenicity and skin elasticity. Methods Measurements by ultrasonography B-mode and by Cutometer SEM 575 wer e carried out in the morning and in the afternoon on 20 men and 20 women (m ean age 30 years) on three areas of the face (forehead, corner of the eye a nd cheek), the forearm and the upper arm, and the flank, thigh and calf. Results From the morning to the afternoon, the skin thickness in both sexes significantly decreased on three areas of the face, the forearm and the up per arm, but significantly increased on the thigh and calf. In parallel, th e echogenicity significantly increased from the morning to the afternoon on the three areas of the face, the forearm and the upper arm. but decreased significantly on the thigh and calf. Measurements of mechanical properties at four sites demonstrated that from the morning to the afternoon, the majo r parameters of skin elasticity Ue* and Uf* increased significantly in both sexes on two areas of the face and slightly on the forearm. but decreased significantly on the calf. Conclusions The diurnal profiles of skin thickness and skin elasticity in t he upper half of the body are the reverse of those in the lower half of the body. These findings suggest that shifts of dermal fluid from the face to the leg by gravity during the day cause the diurnal variation in skin thick ness.