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j. Soc. Cosmet. Chem., 40, 335-346 (November/December 1989) Development of a novel hybrid powder formulated to quench body odor FUJIHIRO KANDA, EIICHIRO YAGI, MINORU FUKUDA, KEISUKE NAKAJIMA, TADAO OHTA, and OKITSUGU NAKATA, Shiseido Research Center, 1050 Nippa-cho, Kohoku-ku, Yokohama, Japan 223. Received June 2, 1989. Presented at the 15th IFSCC Congress, London, September 29, 1988. Synopsis Olfactory and instrumental analyses show that short-chain fatty acids contribute to both foot and axillary malodors. The mechanism of choice to quench short-chain fatty acid malodors was to convert volatile short-chain fatty acids into their corresponding nonvolatile odorless metallic salts. Several metal-containing candidates were evaluated by means of headspace gas chromatography (HS-GC) for their ability to efficiently quench short- chain fatty acids. Zinc oxide was found most suitable for this purpose. Despite its strong deodorizing power, due to its aggregating ability, shortcomings such as clogging of aerosols and rough texture are unavoidable when formulating zinc oxide into deodorant products of various forms. By forming a hybrid powder in which zinc oxide is uniformly covered on the surface of a spherical resin such as nylon, these shortcomings were overcome without sacrificing any deodorizing power. Body odor quenchers formulated with this hybrid powder were more efficacious than conventional antiper- spirants and deodorants on both foot and axillary odor. INTRODUCTION Regardless of sex, age, or race, people have always been sensitive in trying to eliminate offensive body odors as much as possible. To fulfill such demands, countless products by various manufacturers have appeared in the marketplace. Human body odors result from interactions between secretions of eccrine, sebaceous, and apocrine glands, and resident bacteria. Several approaches have been made to control body odors, out of which the antiperspirants and antimicrobials have been most successful. Antiperspirants inhibit perspiration by means of aluminum salts, and antimicrobials inhibit odor- forming bacteria. Nevertheless, such ingredients are intended to prevent the generation of body odors and generally have little effect in reducing malodor once formed. Body odors have been investigated in terms of chemical compound constituents by dermatologists and analytical chemists, but little is still known as to which chemical compounds are responsible for the malodor for specific body sites. We have recently 335