In the future, hair dye may actually smell good. Photo: Getty Images

Hair dye stinks. Period.

Unless you are using the gentler (and less effective) no-ammonia versions, the industrial cleaner smell is just an unfortunate part of the process.

Until now. According to Scientific American, L'Oréal has invented an odorless ammonia substitute called INOA (which stands for Innovation No Ammonia). New technology allows for the compound to penetrate deeper into the hair than traditional no-ammonia formulas, allowing permanent coverage, even on grays.

And L'Oréal scientists have observed that the new formula doesn't weaken hair as much as traditional ammonia formulas.

But the new ingredient is controversial.

Just because the stinky odor is gone, that doesn't necessarily mean it's a healthier product. There are longstanding concerns about work-related asthma in people who are exposed to chemicals like ammonia and monoethanolamine (a component in INOA).

Rebecca Sutton, a senior scientist at the Environmental Working Group, told Scientific American: "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 odor."

INOA is available in Europe and will be coming to the US during the first part of 2010.

Also in 2010, Garnier is introducing Herbashine, an ammonia-free formula that smells like fruit -- not bathroom cleaner.