For the past four years, some celebrities and fashionistas with $250 to $600 to drop at a hair salon have raved about “Brazilian-style keratin” hair straighteners purported to transform frizzy, unmanageable hair into flat, silky-smooth locks.
In fact, those chemical concoctions are loaded with formaldehyde, which numerous prestigious health bodies, most recently, a National Academy of Sciences panel, have labeled a human carcinogen. Formaldehyde is also a potent allergen. It is especially hazardous when it reverts to its natural state, a gas, and is inhaled. Formaldehyde-based hair straighteners present a particular danger to salon workers who apply blow driers and 450-degree flatirons to chemical-coated hair.