The anti-virus activity of surfactants is well known, it is said that attributed to the strong action for the outer coat capsule protein of the virus.^{\cite{Gerba_2014},\cite{Perinelli_2019}} Recently, a quaternary ammonium salt surfactant was reported to have antiviral activity against SARS-CoV-2.^{\cite{coronavirus}} Our study had revealed that quaternary ammonium salt type surfactants have a strong effect on skin barrier function. Therefore, it may require the scrupulous precautions and, in some cases, restrictions when quaternary ammonium salt type surfactants used. In order to inform this fact as soon as possible and to assist in detailed verification by dermatologists and development of formulations for safe use, I report the effect of quaternary ammonium salt type surfactants on the skin barrier function. This manuscript consists of information on changes in the skin permeability of substances due to surfactants, out of the research that attempted a structural chemistry approach to study the mechanism of the effect of surfactants on the skin barrier function. I hope that this report will be useful in countering the threat of COVID-19.

Figure 1 show the TI values of surfactants containing a quaternary ammonium type surfactant. The TI value is a relative value of a substance's skin permeation rate, and when TI = 1, it indicates that the permeation rate is the same as that of water-wetted skin.^{\cite{Okasaka_2018}} All experimental results were obtained using a 1% (w/w) concentration of surfactant. As detailed in reference article 4, this experiment measures the permeation rate of an indicator substance in surfactant-removed skin after treatment with the surfactant. That is, it should be noted that the skin permeability of the substance is enhanced in the absence of the surfactant.