Testing for irritation with a multifactorial approach: comparison of eightnon-invasive measuring techniques on five different irritation types

Background Non-invasive bioengineering methods are widely used in the asses sment of irritant skin reactions. Objectives To assess the ability of eight non-invasive measurement techniqu es to distinguish changes in skin conditions over time, these changes being induced by five different irritants. Methods The following techniques were compared in a multivariate analysis: laser-Doppler perfusion imaging (LDI), laser-Doppler flowmetry (EDF), trans epidermal water loss (TEWL), visual scoring (VS), colorimetric measurements (Chromameter CR 200 a* and L* scales), Mexameter Hb scale (Mexa Hb) and ca pacitance (Corneometer CM 820). Irritants tested were sodium lauryl sulphat e 2% (SLS), tape stripping (TS), tretinoin 0.05% (TRET), ultraviolet (UV) e xposure to 30 W m(-2) UVB/95 W m(-2) UVA, and dithranol 0.5% (DIT). Measure ments were performed at baseline and after 24, 48 and 72 h. The study was c onducted on the upper back of 11 healthy volunteers of both sexes aged 27-3 1 years. Results For DIT it was possible to discriminate over time with CR 200 a* an d L*, VS, LDI, LDF and Mexa HE In SLS discrimination over time was seen wit h TEWL and LDF. Discrimination in TS was demonstrated for TEWL, VS, CR 200 a*, CM 820, LDF, LDI and Mexa Hb. In TRET discrimination ability was seen f or LDI, LDF, Mexa Hb and VS. For UV it was possible to discriminate using V S, TEWL, LDF, LDI and Mexa Hb. Conclusions Different irritation patterns need different measurement modali ties in order to give optimal discrimination over time.