Skin irritation in man: a comparative bioengineering study using improved reflectance spectroscopy

Publisher Website
Google Scholar
Abstract
Variable types of skin irritation were induced in 8 human female volunteers, ranging from subclinical to visible erythema with slight oedema. Skin reactions were graded clinically and objectively using transepidermal water loss (TEWL), laser Doppler flowmetry (LDF) and improved reflectance spectroscopy. This last technique enables separation of in vivo erythemas into relatively deoxygenated (venous‐deoxy hem) and oxygenated (arterial oxy hem) haemoglobin components. Compared to uninvolved skin, an empty patch increased oxy hem by 197%± 121%(p < 0.05). Exposure to vehicles also changed skin biophysics. At sodium lauryl sulfate (SLS) and hydrochloric acid (HCL) exposed sites, a linear correlation between concentration and oxy hem. LDF and TEWL was found. These chemicals predominantly increased TEWL values. Nonanoic acid (NON) and imipramine (IMI) also raised oxs hem, LDI and TEWL values linear at increasing concentrations. Although IMI 2.5% clinically was graded as a type ++ response, no significant increase in TEWL was found. The improved reflectance spectroscopic technique proved valid in skin irritation studies, with a higher sensitivity than laser Doppler flowmetry, and allowed irritant vascular reactions to be discriminated into arterial and venous components. Furthermore, our observations clearly demonstrate that clinical indistinguishable skin irritation reactions induce significantly different changes in barrier function (disruption) and vascular status.