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j. Soc. Cosmet. Chem., 46, 53-65 (January/February 1995) A new noninvasive method to evaluate the antipruritic efficacy of over-the-counter skin care products CURT WEINSTEIN, Pharmaceutical and Cosmetic Evaluations, Danbury, CT 06811, RONALD DROZDENKO, Pharmaceutical and Cosmetic Evaluations and Western Connecticut State University, SIDNEY WEINSTEIN, Neurocommunication Research Laboratories, Inc., Danbury, CT, and HOWARD SPIVAK, Varvak Computing, Inc., Brooklyn, NY. Received August 2, 1994. Synopsis Mild-to-moderate pruritus can be validly and reliably induced nonchemically by means of an itch esthe- siometer comprising a set of calibrated nylon monofilaments. This patented itch esthesiometer is related to another instrument that is used extensively in diagnoses of neuropathology. This paper presents a brief overview of the literature on itch and itch induction methods. Data are presented that establish the reliability and validity of the new procedure, thereby enabling the measurement of antipruritic efficacy. In contrast to other methods, the itch esthesiometer induces itch without discernible wheal or flare. Further, the itch elicited is sufficiently brief to allow the time course of antipruritic action to be determined. Therefore, by using this procedure, it is possible to measure the effects of antipruritic agents on mild itch, simulating conditions such as dry skin itch or itch mechanically induced on mildly irritated skin. Exper- iments are reported that show the antipruritic efficacy of both a moisturizing vehicle (oil-in-water) and a topical anesthetic (benzocaine). INTRODUCTION The literature on itch, while extensive, still leaves many incompletely answered ques- tions. Although there has been considerable research on the anatomy, physiology, and psychophysiology of itch (for reviews see references 1-3), it has been difficult to relate clearly anatomy and physiology to sensation and perception. Sinclair (4) stated that the clinical testing of pain and itch were unsatisfactory. He argued that electrical, temperature, or chemical methods to induce itch or pain tend to arouse other sensations as well, because no pure stimulus for these sensations exists. The literature indicates that there are a few paradigms for inducing itch. Early work by Titchener (5), working with hairs, describes low-intensity stimulation producing itch and higher-intensity stimulation producing pain. Chapman et al. (2) reported that itch can be induced by electrical stimulation, thermal radiation, cowhage (i.e., itching powder), light repeated pin pricks, vasodilation (chemical or ultraviolet light induced), 53