Traditional visual reading of patch-test reactions is a rather subjective method, lacking the sensitivity and reproducibility needed in experimental studies. Recently the laser Doppler perfusion imaging (LDPI) has been used to measure objectively the increase in superficial blood flow which results in the appearance of erythema.

We designed this study to examine the relationship between the LDPI measurement and visual reading after patch test to several different irritants.

In this study, reading of erythema in experimentally-induced irritant contact dermatitis was performed visually and by laser Doppler perfusion imaging (LDPI). In addition, we investigated whether the LDPI measurement was appropriate in the routine patch test clinic.

A close correlation was shown between the 2 methods (r=0.9046, p<0.001) and the LDPI producing mean adjusted perfusion values (APVs) was able to discriminate between the different visual grades.

LDPI is a valuable instrument to objectively assess intensity of irritant patch-test reaction, and is indeed one of the few methods which overcomes the inter-individual variations in visual reading, but this instrument is not appropriate to use routinely in patch test clinic because of unacceptably long measurement time.