This is a link to an older article, but I really appreciate the unbiased comparison between MEA and ammonia in hair color. It also covers the fact that for any hair color that is used that lifts and deposits, there has to be some form of alkalizing agent. No hair color can be chemical free and still work. It’s my personal opinion that MEA based color is much gentler and safer than ammonia based color based on the simple fact of less skin irritation and no harsh fumes.

https://organichaircolorreview.wordpress.com/2013/01/03/mea/