J. Sot.. Cosmetic Chemists, 17, 789-800 (1966) The Action of Antiperspirants CHRISTOPHER M. PAPA, M.D.* Presented May 10, 1966, New York City Synopsis--Stripping experiments, methylene blue iontophoresis, and histological studies after induced sweating indicate that formaldehyde forms a physical plug in the sweat duct. On the other hand, similar experiments with aluminum chloride treated skin suggest that this antiperspirant acts by altering the permeability of the sweat duct. Our fastidious population indulges in a significant amount of con- cern about those usually private recesses, the axillae. Women require the area be denuded of hair, and both sexes apparently wish the under- arms dry and odor free. While cold steel swiftly decides the fate of the useless pelage, the chemical attack on axillary perspiration remains un- sure. If the compound to be applied has bacteriostatic properties, it will succeed as a deodorant since it retards the microbial growth which produces the offensive odor (1). Usefulness in sweat suppression, how- ever, is a more vexing problem. The eccrine sweat glands contribute the major portion of secretory products in the axilla. Therefore, interest has centered on chemicals which might produce anhidrosis, interference with the production or delivery of sweat to the skin surface. Both formalin and aluminum salts have been employed for this purpose for some time, without sure knowledge of their modes of action. The popular concept is that both * Department of Dermatology, University of Pennsylvania, School of Medicine, Phila- delphia, Pa. 19104. Research supported by the U.S. Public Health Service, Postdoctoral Fellowship No. F2-AM-15-48801. We are indebted to the inmates of Holmesburg Prison for serving as volunteers and to the administration (Edward Hendrick, Superintendent) for use of the facilities. 789

790 JOURNAL OF 'FILE SOCIETY OF COSMETIC CHEMISTS Figure 1. Anhidrotic square of skin following treatment with 10rf formalin solution. The lower half of the area has been striI)pcd to remove stratum comeurn using cello- phanc tape. Following thermal stimulation sweat ap- pears in the stripped area only as the superficial obstruc- tion is relieved. The skin has been painted with a starch- castor oil suspension, and the perspiration shows as white droplets produce some type of plug at or near the skin surface, occluding the eccrine ostium and preventing the exit of perspiration (2, 3). Formalin introduced into the skin by iontophoresis has also been reported to inhibit glandular secretion directly (4). Unable to find evidence for plugging, Sulzberger, et al. suggested that aluminum worked in an en- tirely different manner. An inflammatory infiltrate, found about the intraepidermal and high derreal portions of the duct, was thought to interfere with transport of the sweat (5). This action was said to result from "cherootaxis." By the use of sensitive in ,,itro studies, however, Blank, et al. concluded that aluminum did not penetrate into derreal tis- sue (6). It was with the hope of resolving these contradictory views that the following study was initiated. EXPERIMENTAL Production of Anhidrosis Twenty healthy men served as subjects. Square gauze pads (5 cm), with either 10% formalin, 20% aluminum chloride (hexahydrate), or distilled water, were placed on the volar surfaces of forearms under an occlusive dressing of Saran Wrap •"•* and Clear Tape •'t overnight for 18 hours. Following removal of these patches, the men were exposed to