Spatial variations in forearm skin tissue dielectric constant

Background: Tissue dielectric constant (TDC) values measured at 300 MHz via the open‐ended coaxial line reflection method depend on the effective measurement depth and the anatomical site being evaluated. Measurements on the forearm have shown that the TDC values decrease with increasing measurement depth but the spatial variability of the TDC values among forearm anatomical positions is unknown. Our goal was to characterize the extent of such spatial variations. Methods: In 30 healthy seated women (27.4±6.5 years), TDC was measured on the forearm midline and 1.2 cm medial and lateral to the midline at sites 4, 8 and 12 cm distal to the antecubital crease. Results: The midline and medial TDC values increased progressively from 4 to 8 to 12 cm sites (P<0.001), with the largest spatial gradient along the midline. At a depth of 2.5 mm, the TDC values increased from 26.3±2.8 to 27.4±3.4 to 28.4±3.7, with a maximum difference of 8.2±10.6%. For all sites, the TDC values were significantly (P<0.001) less for increasing depths. Conclusion: The findings reveal increased TDC values along the forearm from proximal to distal, most prominent at the midline and medial positions. Because many skin‐related dermatological and biophysical studies utilize the forearm as a test target, such differences may be important to consider because TDC values in part are reflective of local tissue water (LTW). Although the variation in the TDC values among sites was less than 10%, such differences are of importance when evaluating LTW changes using the TDC method in patients with arm lymphedema that is present in variable arm anatomical locations.     

Local tissue water assessed by measuring forearm skin dielectric constant: dependence on measurement depth, age and body mass index

Background: Tissue dielectric constant (TDC) measured at 300 MHz via the coaxial line reflection method is useful to evaluate local tissue water (LTW) and its change. Because excitation field penetration depth depends on size and geometry of the coaxial probe in contact with the skin, TDC values reflect skin and subcutaneous fat to varying depths depending on the probe used. Because tissue changes that occur with age or body mass index (BMI) may affect tissue water content and its depth distribution, our goal was to use TDC measurements to characterize depth patterns of LTW in normal tissue and to investigate the possible impact of age and BMI.
Methods: TDC was measured to depths of 0.5, 1.5, 2.5 and 5.0 mm on both forearms of 69 healthy women (age: 22–82 years, BMI: 18.7–46.1 kg/m²).
Results: Independent of age or BMI, TDC values decreased significantly with increasing measurement depth (33.7±5.8 at 0.5 mm to 21.8±3.7 at 5.0 mm) but at all depths dominant and non-dominant TDC values were similar to each other with ratios ranging from 1.025±0.081 at 0.5 mm to 1.017±0.097 at 5.0 mm. TDC values only at 2.5 and 5.0 mm decreased significantly with increasing BMI whereas TDC values only at 0.5 and 1.5 mm increased significantly with age.
Conclusion: The findings indicate that normal TDC values are affected differentially by BMI and age in a depth-dependent manner. Possible explanations are discussed.     

Skin barrier response to occlusion of healthy and irritated skin: Differences in trans‐epidermal water loss,erythema and stratum corneum lipids

Background. Occlusion of the skin is a risk factor for development of irritant contact dermatitis. Occlusion may, however, have a positive effect on skin healing. No consensus on the effect of occlusion has been reached. Objectives. To investigate skin barrier response to occlusion on intact and damaged skin. Methods. In study A, the response to occlusion (nitrile glove material) for either 8 hr daily for 7 days or for 72 consecutive hours, respectively, was determined and compared with that of non‐occluded skin. In study B, the response to occlusion of for 72 consecutive hours of skin that had been damaged by either sodium lauryl sulfate (SLS) or tape stripping, respectively, was determined and compared with that of to non‐occluded pre‐damaged skin. Skin barrier function was assessed by measurements of trans‐epidermal water loss (TEWL) and erythema. In study A, stratum corneum lipids were analysed. Results. Occlusion of healthy skin did not significantly influence skin barrier function, ceramide profile or the ceramide/cholesterol ratio. Occlusion of the skin after SLS irritation resulted in higher TEWL than in the control (P = 0.049). Occlusion of the skin after tape stripping resulted in lower TEWL than in control skin (P = 0.007). Conclusions. A week of occlusion did not significantly affect healthy skin, but was found to decrease healing of SLS‐damaged skin, and to improve healing of tape‐stripped skin.     

ROAT: morphology of ROAT on arm, neck and face in formaldehyde and diazolidinyl urea sensitive individuals

The morphology of early allergic contact dermatitis reactions was studied in formaldehyde allergic individuals exposed to a cream product preserved with 4 different concentrations of diazolidinyl urea. The study was made using a dose-escalating design in 3 different anatomical regions, the upper arm, neck and face. On the arm and neck, the dominant initial morphology was an eczematous papular eruption. In the face, the initial skin changes were more homogeneous and infiltrated erythema.     

Effect of oral intake of choline-stabilized orthosilicic acid on skin,nails and hair in women with photodamaged skin

Chronic exposure of the skin to sunlight causes damage to the underlying connective tissue with a loss of elasticity and firmness. Silicon (Si) was suggested to have an important function in the formation and maintenance of connective tissue. Choline-stabilized orthosilicic acid (“ch-OSA”) is a bioavailable form of silicon which was found to increase the hydroxyproline concentration in the dermis of animals. The effect of ch-OSA on skin, nails and hair was investigated in a randomized, double blind, placebo-controlled study. Fifty women with photodamaged facial skin were administered orally during 20 weeks, 10 mg Si/day in the form of ch-OSA pellets (n=25) or a placebo (n=25). Noninvasive methods were used to evaluate skin microrelief (forearm), hydration (forearm) and mechanical anisotropy (forehead). Volunteers evaluated on a virtual analog scale (VAS, “none=0, severe=3”) brittleness of hair and nails. The serum Si concentration was significantly higher after a 20-week supplementation in subjects with ch-OSA compared to the placebo group. Skin roughness parameters increased in the placebo group (Rt:+8%; Rm: +11%; Rz: +6%) but decreased in the ch-OSA group (Rt: −16%; Rm: −19%; Rz: −8%). The change in roughness from baseline was significantly different between ch-OSA and placebo groups for Rt and Rm. The difference in longitudinal and lateral shear propagation time increased after 20 weeks in the placebo group but decreased in the ch-OSA group suggesting improvement in isotropy of the skin. VAS scores for nail and hair brittleness were significantly lower after 20 weeks in the ch-OSA group compared to baseline scores. Oral intake of ch-OSA during the 20 weeks results in a significant positive effect on skin surface and skin mechanical properties, and on brittleness of hair and nails. An erratum to this article can be found at     

Biophysical measurements of human forearm skin in vivo: effects of site, gender, chirality and time

Background/aims: Measurements of transepidermal water loss (TEWL) and skin colour are biophysical techniques commonly used to measure the in vivo skin effects of cosmetics, topical medicaments and chemical irritants. The purpose of this study was to investigate the variability of TEWL and skin colour on human forearm skin as a function of regional variation, gender and preferred chirality over an 8 h period.
Methods: Biophysical measurements of TEWL and skin colour were made at five sites on both forearms of male ( n =8) and female ( n =9) human volunteers in vivo (38% relative humidity, 21°C).
Results: Rates of TEWL at the forearm midpoint were 10% lower than at the forearm extremities ( P <0.01). Skin redness ( a *) near the wrist was 5–10% higher than at other sites ( P <0.05). Rates of TEWL were 5% higher in male volunteers ( P <0.05). Red and blue ( b *) colour measurements of male forearm skin differed by 18% and 20% in comparison with female, respectively. Rates of TEWL, skin brightness ( L *) and b * decreased by 9% ( P <0.05), 1.8% ( P <0.05) and 4% ( P <0.05), respectively, with time whereas a * and skin temperature increased by 4.5% ( P <0.01) and 7.2% ( P <0.01), respectively. There was a significant correlation between the change in all measured parameters with time.
Conclusions: Significant differences in TEWL and skin colour were identified that may have relevance in the design and interpretation of multivariate analyses of human forearm skin. Diurnal variation of TEWL, skin colour and temperature may have a single underlying mechanism.