Evaluation of a quantitative clinical method for assessment of sensory skin irritation

Sensory skin irritation refers to the myriad of symptomatic complaints (e.g ., sting and burn) frequently associated with inflammatory skin conditions or skin intolerance to various chemicals or finished products. Sensory irri tation is an important factor in consumer acceptance of the products that t hey buy and use; however, from a safety testing and risk assessment standpo int, it has been difficult to evaluate. Recently, methods have been develop ed to more quantitatively assess sensory irritation using a semantically-la beled scale of sensation intensity, the labeled magnitude (LM) scale. Using this device, studies were conducted to determine if test subjects' percept ions of recalled or imagined sensory responses (from a series of survey que stions) were related to their actual sensory reactivity to chemical challen ge. Subjects were presented with 15 skin sensation scenarios of varying int ensities and asked to record their self-perceived recalled or imagined resp onses using the LM scale. Individual and mean responses to each of the 15 s urvey questions were compared within and across studies. Considerable varia tion was seen between subjects' responses to the questions, particularly fo r questions pertaining to stronger stimuli (e.g., scalding water or skin la cerations). There was also little consistency seen in the pattern of indivi dual responses across the questions. However, among 4 different study popul ations, the group mean scores for each of the 15 survey questions showed a high degree of consistency. Also, in spite of the variability in perceived responses to the recalled/imagined skin sensations, statistically significa nt dose-response and time-response patterns were observed in chemical (lact ic acid and capsaicin) challenge studies. In one capsaicin study, a direct relationship was observed, among 83% of the study subjects, between the mea n recall intensity scores and actual responses to subsequent capsaicin chal lenge. This pattern was not seen in a lactic acid challenge study. However, a similar relationship was seen in this study if only recall stimuli relat ed to sting-type responses were included in the analysis. Hence, use of rec all/imagined skin sensation perception data for prediction of actual reacti vity to chemical probes may have screening utility depending on the survey questions used. On the whole, the LM scale is of practical use for quantify ing subjective sensory irritation responses. Combined with evolving noninva sive instrumental and bioassay procedures for identifying biophysical or in flammatory markers of sensory irritation, better methods are on the horizon for improving our sensory skin irritation testing and risk assessment capa bilities. (C) Munksgaard, 2001.