You know that distinct smell you notice as soon as you walk into a hair salon? That's ammonia1, a colorless chemical used in dyes—and okay, maybe a bit of hair spray. The fumy substance can make your eyes, nose, and throat burn, and if that's not bad enough, it can also fry your hair.
Ammonia helps the hair accept permanent color and can support the lightening process—but is it really necessary? Maybe not. According to Kate Reid, Design Director and Education Manager at Color Me by Kevin Murphy, there have been exciting improvements in the hair color industry over the last decade, including some standout ammonia-free formulas. Not only does it work just as well as the harsher variety, "but generally, ammonia-free brands consider the quality of ingredients and their impact on the environment," she tells Byrdie.
https://www.byrdie.com/best-ammonia-free-professional-hair-color-348330