Insight into how skin changes perfume.

Synopsis Overall consumer perception of personal products such as colognes, deodorants, talc, and soap is often strongly influenced by the presence and nature of the fragrance incorporated into these products, which is also true for the corresponding olfactory characteristics of skin during and after application. Although extensive research has been carried out to define the morphology and characteristics of living skin, relatively little is known about the physical or (bio)chemical behaviour of perfume once deposited onto skin. It is widely acknowledged that some perfumes may perform very differently on different skins, but little definitive information is available to elucidate the associated mechanism(s). Rationalization of this may necessitate understanding both the physical and the chemical interactions between perfume and skin. To assist studies in this area, techniques based on headspace analysis and solvent swabbing have been developed to monitor fragrance concentrations on and above skin in use. Using these techniques, we have carried out some initial exploration into the physical and chemical interactions between skin and perfume. (a) Physical interactions: differences in perfume behaviour when on skin and when on a relatively inert surface (vitreous tile) were quantified to build up at least a qualitative idea of the importance of physical interactions between skin and perfume. (b) Chemical interactions: the potential for skin-mediated chemical transformation of perfume was examined across a wide range of functional groups relevant to perfumes, but was found to be low under 'non-forcing'conditions (i.e. clean dry skin). However, some evidence has been found for changes in perfume ingredients in the underarm, probably arising from microbially catalysed reactions. It is envisaged that it may be possible to harness such transformations usefully - for example, to deliver unusual fragrance effects or enhance fragrance longevity. In addition, product-mediated transformation on skin is feasible, and a specific case has been investigated based on the pH sensitivity of citral acetalization.