In nail care, it may come as no surprise that “formaldehyde may also cause skin irritation, as well as allergic reactions to this ingredient,” as stated by the FDA.
Notably, California is not banning all formaldehyde-releasing preservatives — of which there are many — from products. Quaternium-15, for example, will no longer be allowed, but others are not on the list.
Why it’s used: Formaldehyde is an effective preservative (there’s a reason it’s in embalming fluid) and it is antibacterial. In hair straightening products, Allure has previously reported that formaldehyde locks hair into a straighter position that lasts beyond shampooing. And in nail strengtheners, formaldehyde is supposed to bond with the nail’s keratin. “Using these nail hardeners often, however, may make nails brittle and more likely to break or peel,” cautions the FDA.
What brands could use instead: Other preservatives do indeed exist — sodium benzoate, phenoxyethanol, and caprylyl glycol are three options — but “each has its own benefits and limitations in use,” says Dobos. While formaldehyde-releasing preservatives tend to be “effective over a broad range of bacteria and some are also active against fungi (yeast and mold),” other preservatives often are only effective against “gram-positive bacteria, gram-negative bacteria, yeast, or molds” and they may require low-formula pHs in order to work, “which isn’t deal for a lot of skin-care products,” explains Dobos. Short-chain parabens are effective like formaldehyde donors, “but negative perceptions have really removed those from the formulators tool kit,” she says.
In nail polish and nail care, “alternatives used today include toluenesulfonamide/epoxy resin (TSER), polyester resins, and methylsulfonylmethane,” says Dobos.
And in hair care, “thioglycolates are ingredients used in hair relaxers that are long-lasting, at least until the hair grows out. This is the same ingredient used in perms which breaks bonds in the hair and allows them to be reset,” says Dobos.
PFAS “Forever Chemicals”
Where you’ll find them: PFAS (which stands for Per- and Polyfluorinated Substances) is the umbrella term that refers to the hugely controversial category of “forever chemicals,” which are most commonly found in products that are not cosmetics, like stain-resistant fabric and carpeting, cleaning products, paint, firefighting foam, nonstick cookware, wire insulation, and more. PFAS may also be in beauty products — “things like long-lasting makeup; foundation, and mascara,” says Romanowski. Perfluorooctyl triethoxysilane and perfluorononyl dimethicone are two kinds of PFAS “that have been used in cosmetics, but have been reformulated out of many brands already,” adds Dobos.