I don't know how many times in the past (before I knew better) dyed my hair with box retail dye and had a horrendous reaction to chemicals that were in the hair color. I had anything from chemical burns, sores, itching, rash, headaches and my hair smelled horrible for days. Researching all the chemicals that have been in color hair dyes for years is enough to make you wonder why it's still legal to throw the crud into a mixture that you would apply directly to your head (which is one of the quickest ways into your bloodstream). Below are some excerpts I found on the topic.
I know that it seems like everything causes cancer these days, but that is because our systems are so overloaded from years of us and our parents using these chemicals on our/themselves that we just can't take it anymore. Something has got to give. Think about it, would you shoot formaldehyde, ammonia or heavy metals into your bloodstream via an IV?? Then why would you put it into your blood stream by applying it to your largest organ that wicks up anything you apply to it like a sponge?
Funny how people forget that your skin can soak up things that you think it wouldn't; remember PCP people? I once heard a story from my physician about when he was in the service and the govt, was experimenting with the use of PCP. He apparently had some that was applied to his flight jacket and never knew it. Every time he wore the jacket he started to hallucinate and feel weird. He never put the two and two together for awhile and someone else brought it to his attention and told him to get tested (since they thought he'd been poisoned) they did blood work on him and found the drug in his bloodstream. Then he wondered where he came into contact with the drug and realized that he felt that way every time he put that jacket on.
Clairol, Revlon, all of the box shelf big name brands had a hazard number between 7-10 which was extremely high in toxic chemicals. See below ewg.org link below. Save that website and you can freak out about all the chemicals you unknowingly use on a daily basis. I do of course like to use products that work and sometimes I breakdown and have to use the old standard, but I try not to make it habit and that's good enough for my eco trained health conscience.