ACTION OF ANTIPERSPIRANTS '2: '• •: ':i"'::"•"•: 791 Figure 2. Area of wfiar forearm treated with aluminum chloride solutiou remains auhidrotic even though the lower half has beeu stripped to remove the horuy layer. It would thus be unlikely that a superficial block is operatiug iu this iustance. The few sweat puucta appearing in the stripped site reflect the uumaskiug of the auhidrosis pro- duced by the aqueous vehicle 38 øC and 90% relative humidity in a controlled heat chamber. Sweat- ing was demonstrated by painting a starch-castor oil mixture over the skin droplets of perspiration are observed as white puneta on the sur- face (7). Initially all treated areas are anhidrotic, but within an hour the water site gradually recovers sweating as the skin dries. All subse- quent test procedures in the formalin and aluminum areas, therefore, were carried out only after allowing time for the effects of simple hydra- tion to disappear. When undisturbed, the aluminum and formalin anhidrosis was complete for 3 to 4 days, slowly returning to normal within 7 to 14 days. The following experimental maneuvers were then carried out on the anhidrotic sites to determine how each agent had brought about sweat suppression. Itornj' Layer Removal Half of each anhidrotic test site was stripped with Scotch Tape •* until the major portion of the stratum corneum was removed and the "glistening layer" was reached. Coupled with the visual estimation of * Dow Chemical Co., Midlaud, Mich. • Johusou & Johusou, New Bruuswick, N.J. { Minnesota Miuing Co., St. Paul, Miuu.

792 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 3. Methylene blue pattern produced by ionto- phoresis into normal skin. This is the typical, specific pattern nor•nally obtained. Each punctmn represents passage of dye down the duct and diffusion into the sur- rounding epidermal tissue sweating, this technique immediately demonstrates whether a superficial plug is actually present. Removal of the horny layer to relieve such blockage would allow prompt return of normal sweating. Stripping of both the water and formalin treated sites brings perspira- tion back to the previously dry skin (Fig. 1). The aluminum-salt treated area of anhidrosis, on the other hand, showed little except a few droplets, representing no more than reversal of residual hydration effect (Fig. 2). The tentative conclusion was that formalin and water did actually produce some type of block within the stratum corncure, while the cause of aluminum anhidrosis was deeper in the skin. Methylene Blue Iontophoresis When methylene blue dye is introduced into the skin by iontophore- sis, a typical punctate pattern develops which is entirely localized about the eccrine ducts (Fig. 3). This staining represents transport of the dye down the eccrine ducts and diffusion through the duct wall into the