Title: Bioavailability of scarred skin during application of a vaso-active substance 

Background 
The skin acts as a mechanical barrier in physiotherapy interventions. Although topical applications are frequently used in physiotherapy the evidence of effectiveness is poor or lacking in normal skin research and even more in scar research. The integrity of the skin barrier can be instrumentally evaluated by means of skin hydration and trans epidermal water loss (TEWL). Non-invasive quantification of the skin after penetration of vaso-active substances can be carried out instrumentally, measuring skin color. 

Objectives
In this study, non-invasive skin measurements were used to evaluate bioavailability of scarred skin during application of a vaso-active substance.

Method
Two groups consisting of 19 scar sites and 13 healthy skin sites were selected based upon predefined in- and exclusion criteria. Baseline measurements on a 6 cm2 scar/skin site included colorimetry, TEWL, stratum corneum water content and -distribution and epidermal and dermal thickness with Ultrasound. A filter disk saturated with a Methylnicotinate (MN) solution (0.005M) was applied for 30 seconds on the marked scar/skin site. Bioavailability was assessed by quantification of an MN-induced erythema observed with the Chromameter® after 5, 15, 25, 35, 45, 55 and 65 min. 

Results
A significant difference between both groups was found for the sum of total color change (p=0,02) and for dermal thickness (p<0,0001). The correlation between the latter parameters was significant (rs=-.760, p<0,0001). Hydration values of the Corneometer correlated significantly with moisture distribution and micro-topography of the skin measured with Moisture Map® MM100 (r=.462, p=0,046).

Discussion & Conclusion
The effects correlated significantly with the thickness of the dermis. The role of dermal thickness can be explained by the localization of the skin blood vessels within this layer. The Moisture Map® can be used as an assessment tool for moisture distribution and skin micro-topography, based upon the current primary study results.