Unless Bigen has been changed recently, it is a hair dye with the most highly concentrated amounts of para-phenylenediamine (PPD to be found in hair dyes. You might want to do a Yahoo search on Phenylenediamine and contact dermatitis. It can be pretty nasty stuff with consequences that include skin outbreaks (rashes) to causing irreversable sensitivity to all dyes to potential internal damage. Most permanent hair dyes have some degree of phenylenediamine in them...Bigen has the motherlode.
Bigen is often the black hair dye of choice of people who make "Black Henna" designs on skin that frequently cause mild to severe skin reactions and sometimes more long term damage.
I used Bigen years ago. It colored my hair a wonderful black. But I found it overtime to make my hair feel more brittle and eventually to leave my hair more reddish colored as the black wore out. Which is strange since I was putting Bigen on black hair to make it more black.
Just to say, check out what is listed as the ingredient in Bigen and if it is still the same para-phenylenediamine (PPD...please read up on the potential harm (short-term and long-term) of its use beyond its effect on hair.
The issues with Bigen can be less about what is not in it, as the product information relates, and more about what it is in it.
HennaJoy