Perfumes are complex mixtures of substances dissolved in alcohol or other media and provide a variety of olfactory sensations to the wearer and those in the vicinity. The perfume's scent profile and its evolution over time depends not only on the aromatic components present, but also on their interaction with molecules on the surface of the user's skin, the skin's pH, humidity and temperature. That perfume ingredients can also influence the function of the user's enzymes has been reported by members of the Laboratory of Molecular Carcinogenesis and Drug Development and the Laboratory of Biomolecular Structure and Function in a new paper in the peer-reviewed journal Cosmetics.
In the paper, the authors randomly selected 10 perfumes and showed that all of them, to varying degrees, have a negative effect on the conversion of the male sex hormone testosterone to the female sex hormone 17β-estradiol, and thus some of the perfumes’ ingredients fall into the category of endocrine disruptors. Strikingly, users may not be aware of the presence of such substances even after they have thoroughly examined the perfume composition, as some of the compounds contained are usually shrouded in the veil of trade secrecy. Further, if the skin is exposed to sunlight after perfume application, additional compounds with a higher inhibitory effect on testosterone conversion can (and, as the authors showed, do) form by photochemical reaction. On top, the perfume causing the highest degree of inhibition was shown to affect an enzyme of the cytochrome P450 family - aromatase - not the other enzyme required for catalysis - NADPH:cytochrome P450 oxidoreductase. Overall, the results raise the question whether the current methods of assessing the risks associated with repeated human exposure to mixtures of ingredients in personal care products are sufficient.