Late last year, stylists in the US state of Oregon complained of eye irritation, nosebleeds and breathing issues after repeatedly applying Brazilian Blowout, a liquid keratin straightening treatment.
Oregon's Occupational Safety and Health Administration tested 105 samples of various hair-smoothing products and found unsafe amounts of formaldehyde in all but three brands of them.
The presence of formaldehyde is significant, said Arthur Grollman, a science professor at Stony Brook University School of Medicine.
"My concern is that formaldehyde is a probable human carcinogen that should never touch your skin or anything else," Brisbane Times quoted him as saying.
But despite the nasty buzz on the expensive process, many women seem to think that good hair trumps bad chemicals.