Skin irritation typing and grading based on laser Doppler perfusion imaging.

OBJECTIVE

Vasodilation with increased cutaneous perfusion is an essential part of an irritant inflammatory response. The aim of the present study was to investigate the usefulness of the high-resolution laser Doppler perfusion imaging (HR-LDPI) technique for investigating irritant skin reactions. Irritants may elicit clinically different reactions due to different skin penetration profiles and different modes of irritant action on the exposed

METHODS

Twelve subjects were tested on the forearms using 24 h occlusive application of three concentrations of the irritants sodium lauryl sulphate (SLS) and nonanoic acid (NON) and with the topical acne drug all-trans retinoic acid (RA). Cutaneous blood flow at baseline, the increase in cutaneous blood flow and the skin area having increased perfusion were measured on day 2, day 3 and day 5.

RESULTS

Based both on measurement of mean perfusion and area with increased perfusion, it was possible to differentiate between different clinical irritation grades on any study day. The area with increased perfusion exceeded the area with clinically visible skin reactions for irritant reactions of grade 1/2 and above. Irritant reactions for individual irritants could furthermore be typed using HR-LDPI. It was possible to differentiate between vehicle treatment and the different dose levels of the irritant compounds. A correlation was found between clinical scores for the individual irritants and the mean flow and the area with increased flow. The individual irritants could be differentiated due to different time courses of their skin irritation.

CONCLUSIONS

Laser Doppler imaging was found to be an important new method for characterization and grading of the inflammatory response of single exposure irritant reactions. However, standardised study procedures cannot be emphasised enough in order to obtain reliable and useful data.