Huskymom,
Hair dye ingredients have definitely been linked to cancer. And it may cause seizures and death if you eat it:
http://www.japi.org/november_2009/article_03.pdf
There's an ingredient called PPD in many hair dyes that lots of people are allergic to. Who knows what kind of reaction different people could have, especially the extremely sensitive. Lok here:
http://www.medicalnewstoday.com/articles/62324.php
If you are concerned about the chemicals in hair dye and possibly triggering a seizure, most large health food stores have natural, non-chemical hair dyes. The natural dyes don't work quite as well as the chemical kind and aren't "permanent," but they are worry-free.
Try this stuff:
http://www.actnaturals.com/
Here's a review at treehugger.com:
http://www.treehugger.com/files/2008/11/natural-hair-dye-from-act-naturals.php
I'm a little worried about one thing about the ingredients of Actnaturals. They say it uses "smaller" molecules Do they mean nanoparticles? If they do those have been linked to genetic mutation and cancer when ingested or inhaled, though research has shown nanos don't tend to penetrate the skin layer when you just use it on your skin. Actnaturals also use "natural mineral salts," which could mean aluminum. So I guess nothing is perfect.
For all dyes, be sure to read the label to see if they have chemicals. Any product that says Natural and also "permanent" will also have chemicals in it. (can't be permanent without chemicals) The ones with peroxide are okay - peroxide tends to be nontoxic. But if it has peroxide it probably has artificial oxidative dyes in it, too. And even if it doesn't have ammonia, it may have DEA instead, and that stuff is BAD. I can't believe they put that stuff on something that goes on our skin. Here's the material safety data sheet on that stuff:
http://www.huntsman.com/performance_products/NPE/PDFs/MSDS_US/Diethanolamine MSDS US.pdf.
Henna is really good, if you don't have a ton of gray. But it is hard to find a henna that is colored (other than red) that uses strictly plant-based dyes and not chemicals. Again, read the label. And don't mix hair dyes or perms with henna. It can turn your hair green. Ugh.
Here's a website chock full of henna education:
http://www.hennaforhair.com/science/index.html
Here's a link to a natural hair dye recipie. Who knows if it works. It seems to me it would turn your hair green. If anybody tries it, will you let us know?
http://www.pioneerthinking.com/graydye.html
Oops. TMI. (Did I mention that seizures have made me run on and on and on and on and on? Can't shut up sometimes, not even in writing)