Response to the Letter to the Editor

Abstract

Dear Sir, A number of cosmetic ingredients need to be more evaluated in terms of skin penetration. The cutaneous passage of parabens in respect to their lipophilicity and the number of applications was studied during our experiments. The passage of paraben esters had been shown: it was depending on their polarity: the less lipophilic molecules cross the skin more easily than the most lipophilic ones. Our investigation showed that the penetration of these molecules depends also on the number of applications, the passage of paraben esters being increased after each deposit. The aim of our inquiry was to imitate the current usage of cosmetics in daily life (applying many cosmetic products a day, and usually for a long period). Our results are leading to a suggestion that ‘increasing the permeation could provoke, in a long period, an accumulation within fatty tissues’. Thus, our study was an investigation on the cutaneous absorption of paraben esters but not on paraben’s toxicity. According to the comments of Mr Godfrey we would like to clarify some points. Indeed, we agree with Mr Godfrey that our experiments did not demonstrate the accumulation of parabens even after repeated applications, but just an increased permeation. We only suggested that such an increased permeation could lead to an accumulation. The role of metabolic processes and excretion must been taken, in fact, into consideration. Mr Godfrey reminds that parabens are hydrolyzed by esterases present in the skin and refers to the mentioned reference in our paper (1). Indeed, we do not know what occurs in terms of esterases activities in the skin placed within Franz cells. Nevertheless, only a part (and not the totality) of parabens seems to be metabolized (1). In our conclusion, we only indicated that there is a possibility of accumulation. In the second group of experiments (three applications of the lotion), it was done intentionally to imitate the usual usage of cosmetics as it was explained in our paper. Concerning skin integrity after 36 h, a number of studies assessed the cutaneous passage of molecules for more than 24 h: 48 h of investigation (2,3) and 36 h of investigation (4). The aim of our work was to evoke the suspected side effects of parabens and our introduction quoted some references showing the necessity for parabens to be more studied in order to draw conclusions about their toxicity or their innocuity. We understand that Mr Godfrey develops his own analysis about the relationships between parabens and breast cancer. It was absolutely not the aim of our study to explicate such aspect of parabens. Finally, we can understand the position of Mr Godfrey by defending the paraben’s usage in cosmetic formulations. We are grateful to Mr Godfrey for developing some comments about parabens, and this long development shows that the analysis of parabens penetration remains an important issue.