The innovative approach to develop cosmetics for sensitive skin: the relation between preservatives and inflammatory cytokines
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Presented by: Yuko Ito
[Introduction and Purpose]
We have often seen cosmetics for sensitive skin as consumer’s awareness of sensitive skin and the interest of hypoallergenic cosmetics are increasing worldwide in recent years. Preservatives have considered to be one of the causes of skin irritation. As the data to support this fact, in the IFSCC 2020 Yokohama Congress, we have reported that several preservatives, including phenoxyethanol, increase the expression level of inflammatory cytokines, which induce not only the skin inflammatory response but also aging, by activating transcription factors such as nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK). On the other hand, many ingredients which have the same effect as preservatives are used in most cosmetics for sensitive skin. However, there are no reports investigating the expression of inflammatory cytokines induced by alternative preservatives. Thus, in order to maintain the quality of cosmetics for sensitive skin and provide safe cosmetics which anyone can use, it is necessary to carefully consider which preservatives and their alternatives to use. Therefore, we examined the inflammatory cytokines induced by preservatives commonly used in cosmetics worldwide and alternative preservatives. Furthermore, we developed the perfect combinations of preservatives and their alternatives that do not increase the expression of inflammatory cytokines and cause any irritation.
[Method]
Normal human epidermal keratinocytes (NHEK) or three-dimensional cultured epidermal models were treated with preservatives and their alternatives at concentrations that do not affect cytotoxicity. Then, the expressions of inflammatory cytokines were examined by quantitative PCR and productions of various inflammatory cytokines were done by enzyme-linked immunosorbent assay (ELISA). As for the evaluation of preservative efficacy, we used our original method of inoculating the product with bacterium and culturing them to observe the duration until the bacteria died. In addition, by using three-dimensional cultured epidermal models, we evaluated skin irritation induced by preservatives and their alternatives.
[Results]
The expression levels of inflammatory cytokines, such as interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α), were different depending on the time and the type of preservatives and their alternatives. As a result of the preservative efficacy test and skin irritation test, each preservative alone could not maintain the quality of the product or caused skin irritation. However, we have found that some combinations of preservatives and their alternatives can maintain the quality of the product without increasing the expression of inflammatory cytokines.
[Discussion]
The expression of inflammatory cytokines was different depending on the preservatives and their alternatives, suggesting that preservatives and their alternatives should be selected carefully, even though the alternatives are not defined as preservatives. Based on these results, we will elucidate the inflammatory mechanisms of each preservative and its alternatives in the future. Moreover, we will advocate the combinations of preservatives and their alternatives we have found as a low-irritant cosmetic.
We have often seen cosmetics for sensitive skin as consumer’s awareness of sensitive skin and the interest of hypoallergenic cosmetics are increasing worldwide in recent years. Preservatives have considered to be one of the causes of skin irritation. As the data to support this fact, in the IFSCC 2020 Yokohama Congress, we have reported that several preservatives, including phenoxyethanol, increase the expression level of inflammatory cytokines, which induce not only the skin inflammatory response but also aging, by activating transcription factors such as nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK). On the other hand, many ingredients which have the same effect as preservatives are used in most cosmetics for sensitive skin. However, there are no reports investigating the expression of inflammatory cytokines induced by alternative preservatives. Thus, in order to maintain the quality of cosmetics for sensitive skin and provide safe cosmetics which anyone can use, it is necessary to carefully consider which preservatives and their alternatives to use. Therefore, we examined the inflammatory cytokines induced by preservatives commonly used in cosmetics worldwide and alternative preservatives. Furthermore, we developed the perfect combinations of preservatives and their alternatives that do not increase the expression of inflammatory cytokines and cause any irritation.
[Method]
Normal human epidermal keratinocytes (NHEK) or three-dimensional cultured epidermal models were treated with preservatives and their alternatives at concentrations that do not affect cytotoxicity. Then, the expressions of inflammatory cytokines were examined by quantitative PCR and productions of various inflammatory cytokines were done by enzyme-linked immunosorbent assay (ELISA). As for the evaluation of preservative efficacy, we used our original method of inoculating the product with bacterium and culturing them to observe the duration until the bacteria died. In addition, by using three-dimensional cultured epidermal models, we evaluated skin irritation induced by preservatives and their alternatives.
[Results]
The expression levels of inflammatory cytokines, such as interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α), were different depending on the time and the type of preservatives and their alternatives. As a result of the preservative efficacy test and skin irritation test, each preservative alone could not maintain the quality of the product or caused skin irritation. However, we have found that some combinations of preservatives and their alternatives can maintain the quality of the product without increasing the expression of inflammatory cytokines.
[Discussion]
The expression of inflammatory cytokines was different depending on the preservatives and their alternatives, suggesting that preservatives and their alternatives should be selected carefully, even though the alternatives are not defined as preservatives. Based on these results, we will elucidate the inflammatory mechanisms of each preservative and its alternatives in the future. Moreover, we will advocate the combinations of preservatives and their alternatives we have found as a low-irritant cosmetic.