8. PEG

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Polyethylene glycols or PEGs are petroleum derivatives that thicken or soften various cosmetic products. Some PEGs may be manufactured using a process that introduces contaminants like ethylene oxide and 1,4-dioxane. As the names suggest, these are not something you want in contact with your body since the former is recognized as a human carcinogen, and the latter is suspected to be. PEGs are a two-edged sword in the sense they they also enhance the skin’s ability to absorb, making it that much easier for potential toxins to get into your system.