Ammonia in hair dyes causes the hair follicle to swell to help hair dye penetrate the cuticle and attach or hold on to the hair. Even though we hear about ammonia free products- it’s difficult to say if they are better. Ultimately these products will still use some kind of alkalinizing ingredients to achieve the same result. If you are not using a permanent hair color this is not necessarily important to have as an ingredient. For me- since I’m always in need of covering my relentless grey hair I tend to use semi permanent colors and these do not tend to have ammonia and can be used when needed.