j. Soc. Cosmet. Chem., 36, 435-440 (November/December 1985) The site of antiperspirant action by aluminum salts in the eccrine sweat olands of the axilla RICHARD P. QUATRALE, EILEEN L. THOMAS, and JAY E. BIRNBAUM, American Cyanamid Company, Shulton Skin Care Research Center, 697 Route 46, Clij9on, NJ 07015. Received August 5, 1985. Synopsis The relative sites of antiperspirant activity within human axillary eccrine sweat glands of aluminum chloro- hydrate (ACH), aluminum zirconlure chlorohydrate glycine complex (AZAP), and aluminum chloride (A1C10 were determined by the cellophane tape stripping procedure. Using the starch/iodine method, individual functioning sweat glands were identified prior to antiperspirant treatment, after treatment, and after tape stripping. As had been found earlier in studies of the eccrine sweat glands in the human forearm, A1CI 3 acted most deeply within the duct, whereas the sites of action for ACH and, particularly, AZAP were closer to the skin surface. On average, however, both ACH and AZAP appeared to inhibit perspiration outflow at a deeper level in more individual axillary sweat ducts than they did in forearm ducts. INTRODUCTION In an earlier study, the sites of antiperspirant action within human forearm eccrine sweat glands which had been inhibited by aluminum chlorohydrate (ACH), aluminum zirconium chlorohydrate glycine complex (AZAP), or aluminum chloride hexahydrate (A1CI•) were demonstrated. Comparison of starch/iodine-generated sweating patterns obtained before and after antiperspirant treatment and then after removal of the intra- corneal sweat ducts by the cellophane tape stripping procedure indicated that ACH, and particularly AZAP, functioned relatively superficially. Removal of the horny layer led to restoration of activity of most of the sweat glands previously inhibited by either of these two aluminum salts. In contrast, A1CI3's site of activity was shown to be deeper within the duct in that stripping caused virtually no restoration of sweat gland func- tion (1). The means by which aluminum antiperspirant salts, particularly the polymeric forms, inhibit sweating is believed to be by their forming a physical blockage within the ducts, as suggested by Relier and Luedders (2). Presumably, when this blockage is relatively superficial, tape stripping removes it and p•rmits the restoration of the excre- tory process. For AICI•, antiperspirant activity is also held to be based on the intra- ductal formation of these occlusive casts, as further described by Holzle and Kligman 435

436 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (3). However, inasmuch as AIC13-caused blockage of the sweat duct is more deeply located in most sweat glands, it is much less readily removed. Subsequent histological studies using both transmission electron microscopy and fluor- escence microscopy confirmed the relative location of each of the three antiperspirants in inhibited forearm sweat glands. ACH was found within the sweat duct at the level of the stratum corneum and in a number of instances at the level of the granular layer of the viable epidermis (4). AZAP was found predominantly in the distal-most region of the duct as it passed through the horny layer (5). In confirmation of previous studies (2,3), A1CI3 has been located within the sweat duct at a depth well below the stratum corneum layer (6). The use of the human forearm or the back to study eccrine sweat gland function, particularly to assess the effects of prototype antiperspirants on that function, is time- honored. However, despite the practical value that these sites offer, caution needs to be exercised in extrapolating the findings to eccrine sweat gland function in the human axilla. The purpose of the studies reported here is to establish the relative intraductal sites of antiperspirant activity of the three aluminum-based salts in the eccrine sweat glands of the axilla as a first step in elucidating the means by which antiperspirants function in the human underarm. MATERIALS AND METHODS The technical approaches used in these studies were virtually identical to those de- scribed previously for the forearm studies. Minor variations in the experimental pro- tocol were introduced principally to adjust for the more profuse and rapidly progressing sweating usually encountered in the axilla compared to that found on the forearm. The subjects were adult females. One site (total area: 4 cm 2) in the approximate center of the axillary vault was selected and marked. On Day I of the study, the subject was thermally stressed in an environmental chamber (100øF, 30-35% RH) for 40 minutes while resting supine. At the end of this acclimation period, the test site was blotted dry with absorbent tissue and a thin layer of the starch, castor oil, and iodine mixture was applied to it to display the sweating pattern. Within a few minutes virtually all sub- jects in all instances exhibited a complete puncrate pattern of sweat gland activity at which point the first photographic record was made. Subsequent photographs, at 10 and at 20 minutes after the initial photograph, were also taken. The number of sweat glands found at all three time points appeared to be identical. However, at these latter points, the sweating pattern of many subjects had lost its discreteness and coalescence of the individual sweat droplets was frequently observed. Accordingly, evaluation of the sweating patterns for all subjects was made using the first photograph only. After recording the control (pretreatment) sweating pattern, the starch mixture was removed and the subject was dismissed. The subject returned the following morning (Day II) at which time the axillary test site was relocated using a template. Next, approximately 0.35-0.45 ml of one of the anti- perspirant test solutions was used to saturate the cotton pad component of an imperme- able mylar-backed bandage (Readi-Band ©, Parke-Davis & Co., Detroit, Michigan). The occlusive patch was then affixed to the skin test site and further secured with strips