5. Formaldehyde

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While formaldehyde may not be added directly to cosmetics, some other common ingredients are capable of producing it over time. Formaldehyde is recognized as a human carcinogen, and is used in industrial processes such as the manufacture of vinyl, plastics and resins. Some ingredients that may release formaldehyde are DMDM hydantoin, diazolidinyl urea, imidazolidinyl urea, methenamine, quaternium-15, and sodium hydroxymethylglycinate. Where do they come up with those names?