Structure-Function Correlations in the Mechanism of Action of Key Antiperspirant Agents Containing Al(III) and ZAG Salts.

Aluminum hydrolysis chemistry is an important part of modern society because of the dominance of Al(III) as a highly effective antiperspirant active. However, the century-old chemistry centered on aluminum chloride (ACL) is not comprehensive enough to address all of the in vivo events associated with current commercial antiperspirants and their mechanism of action. The present study aims to address the knowledge gap among extensively studied benchmark ACL, its modified version aluminum chlorohydrate (ACH), and a more complex but less explored group of aluminum zirconium chlorohydrate glycine complexes (ZAG salts) toward understanding the mechanism of action under consumer-relevant conditions. ACH, which is the Al source used in the manufacture of ZAG salts, provides a bridge between ACL and ZAG chemistry. High viscosity and gel formation driven by pH and a specific Al(III) salt upon hydrolysis are considered the criteria for building an in vivo occlusive mass to retard or stop the flow of sweat to the skin surface, thus providing an antiperspirant effect. Rheological studies indicated that ACL and aluminum zirconium tetrachlorohydrex glycine (TETRA) were the most efficacious salt actives. Spectroscopic studies, diffraction studies, and elemental analysis suggested that small metal oxide and hydroxide species with coparticipating glycine as well as various polynuclear and oligomeric species are the key to gel formation. At a given pH, the key ingredients (NaCl, urea, bovine serum albumin, and lactic acid) in artificial sweat were found to have little influence on Al(III) salt hydrolysis. The effects of the sweat components were mostly limited to local complex formation and kinetic modification. The in vitro comparative experiments with various Al(III) and ZAG salt systems offer unprecedented insights into the chemistry of different salt types, thus paving the way for engineering more efficacious antiperspirant systems.

Understanding the microbial basis of body odor in pre-pubescent children and teenagers.

BACKGROUND: Even though human sweat is odorless, bacterial growth and decomposition of specific odor precursors in it is believed to give rise to body odor in humans. While mechanisms of odor generation have been widely studied in adults, little is known for teenagers and pre-pubescent children who have distinct sweat composition from immature apocrine and sebaceous glands, but are arguably more susceptible to the social and psychological impact of malodor. RESULTS: We integrated information from whole microbiome analysis of multiple skin sites (underarm, neck, and head) and multiple time points (1 h and 8 h after bath), analyzing 180 samples in total to perform the largest metagenome-wide association study to date on malodor. Significant positive correlations were observed between odor intensity and the relative abundance of Staphylococcus hominis, Staphylococcus epidermidis, and Cutibacterium avidum, as well as negative correlation with Acinetobacter schindleri and Cutibacterium species. Metabolic pathway analysis highlighted the association of isovaleric and acetic acid production (sour odor) from enriched S. epidermidis (teen underarm) and S. hominis (child neck) enzymes and sulfur production from Staphylococcus species (teen underarm) with odor intensity, in good agreement with observed odor characteristics in pre-pubescent children and teenagers. Experiments with cultures on human and artificial sweat confirmed the ability of S. hominis and S. epidermidis to independently produce malodor with distinct odor characteristics. CONCLUSIONS: These results showcase the power of skin metagenomics to study host-microbial co-metabolic interactions, identifying distinct pathways for odor generation from sweat in pre-pubescent children and teenagers and highlighting key enzymatic targets for intervention.

A comparative clinical study of different hair removal procedures and their impact on axillary odor reduction in men.

BACKGROUND: Axillary hair can influence the development of underarm odor in men. OBJECTIVE: To compare different hair removal procedures and their impact on the effectiveness of standard soap washing (SW) in reducing male axillary odor. METHODS: The axillae of healthy Caucasian males (N = 30; 18-48 years of age) were randomized in a non-crossover, split body design. Two of four axillary treatments were evaluated per subject: clipped with scissors; wet shaved with a razor; waxed; and untreated. Odor evaluations were performed by trained assessors according to the American Society for Testing and Materials organization at baseline (24 h postcontrol SW), immediately, 12 and 24 h following treatment plus SW (Day 1). Further evaluations were conducted immediately and 24 h following SW on Day 2 and Day 3. Mean odor scores were calculated and an analysis of covariance conducted using baseline data as covariate. RESULTS: On Day 1, hair removal by clipping with scissors followed by SW offered no significant improvement in immediate odor control (27.2% reduction from baseline) when compared with SW alone. Both shaving and waxing followed by SW resulted in an immediate, significant reduction in axillary odor compared with SW alone (57.3% and 75.3% reduction, respectively; P < 0.0001). This improvement persisted for 24 h after shaving (P = 0.0682). Further, a single shaving treatment significantly improved the immediate effectiveness of SW on Day 1, Day 2, and Day 3 compared with SW alone (P < 0.05). CONCLUSIONS: Blade shaving of the axillae can optimize the cleansing and odor reducing effectiveness of daily hygiene measures for men without the discomfort associated with waxing.