One major, major complaint about hair dye is the off-putting smell. It's mostly down to ammonia – the ingredient that enables colour to penetrate into the hair shaft.
Since the invention of the first commercial hair colour a lifetime ago (back in 1909 for the fact conscious), hair dye hasn't really changed much; but now, scientists at L’Oréal have discovered a way to make it smell a little sweeter by using an odourless substance called monoethanolamine (MEA). MEA is nothing new; it's actually already used in ammonia-free dye to darken hair within a level, but it hasn't yet been strong enough to lighten or cover grey – until now.
That's because a colour-boosting mineral oil gel has been added to the MEA to make a formulation that L’Oréal has dubbed "Innovation No Ammonia" (INOA). "I can't say that replacing ammonia-based dyes with those containing monoethanolamine is an improvement for public health, though it will cut down on the noxious odour," the Environmental Working Group's Rebecca Sutton told Scientific American.
L’Oréal, however, claims that the INOA leaves the hair in better condition since it doesn't compromise the integrity of the hair quite as much as traditional hair dye. As long as the smell is gone, that's enough for now.