Formulation Development to Enhance the Residual Performance of Antimicrobial Agents on the Skin

Antimicrobial agents are used in deodorants to inhibit the growth of bacteria that transform sweat and sebum secretions into odorous compounds. In this study, we examined the ability of antimicrobial agents to enhance the deodorant effects. We first assessed changes over time in residual amounts of 4-isopropyl-3-methylphenol （ IPMP ） and 2,4,4 ′ -trichloro-2 ′ -hydroxydiphenyl ether （ Triclosan ） on axillary areas following the use of deodorants. The results suggested that the residual performance of Triclosan was significantly higher than that of IPMP. Second, in order to elucidate the causes of these reductions of the agents on axillary areas, we chose several factors and evaluated each contribution ratio. The results suggested that the primary factors were internal skin penetration and transition to clothes through sweat. Finally, we developed a screening meth-od to evaluate the effects of the deodorant keeper that enhanced the residual performance of antimicrobial agents on the skin. The screening revealed that the deodorant keeper required certain characteristics: high molecular weight, high hydrophobicity and high affinity with antimicrobial agents. In the case of the deodorant keeper for IPMP, the polarized sites on the structure of the ingredients led to high affinity for IPMP because the dipolar interaction was enabled.