I have wondered this before, and almost posted this question in the past, but this thread now has me wondering again. If you use any kind of over the counter hair colorant, they are plastered very blatantly with warnings about possible blindness.
So I want to know, through what mechanism do hair coloring products cause blindness? When I searched the Internet myself, all I could find was the story of two women in the 1930s that had an allergic reaction that ended in blindness. There must be morons out there disregarding the labels – what is happening to them? Is it a proven chemical reaction? Is it allergies? I don’t plan to disregard the warnings, but I would like a more detailed reason than “because we said so” - one that strikes the fear of science in my heart.
Hair dyes are designed to color proteins. Eyeballs have proteins at their surface. So hair dyes will color eyeballs. You’ll likely not go permanently blind if you splash some hair color in your eye, but you might have to wait for the top layer of ‘eyeball skin’ to wear off.
Also, the pervading fear of being sued if Something Bad happens, and they didn’t warn you about Something Bad.
This is what gives rise to the lengthy list of side-effcts on medications these days - "May cause chills, night sweats, nausea, diarrhea, constipation, loss of appetite, visual hallucinations, sensitivity to sunlight, sensitivity to ethnic jokes, cardiac arrest, citizens arrest and dizziness.
They’re just covering their butts in case someone gets the stuff in an eye and winds up with a worse outcome than simply having “Sex Kitten Blonde” eyes for a week. “Can’t say we didn’t warn you!” would be the response.
Just means there is health data evidence that at the concentration in the product there are irritant substances that cause effects such as ocular lesions, oedema of the conjunctivae or corneal opacity according to standard tests.
In a product such as hair dye there is an increased likelihood of ocular exposure due to the way it is used, so the companies make sure the labelling is very obvious.
It is a legal responsibliity of the manufacturer to label products in this way.
Also, virtually all commercial permenant dyes contain developer, which is a peroxide solution - usually hydrogen peroxide. Peroxide in your eyes can hurt very badly and may damage your cornea. Non-permenant dyes are generally safe and some cosmetologists will even dye your eyelashes with these.
Though the concentration of the p-phenylenediamine in the product may be such that it does not present irritant health effects. On the other hand there may be additive irritant effects between the p-phenylenediamine and other ingredients to cause the overall mixture to act as a serious irritant.
If you really want to find out, request an MSDS from the manufacturer. I just googled for a generic MSDS but had no luck. The manufacturer or supplier is required by law to provide one to people in the workplace - if say you were a hairdresser. I think this obligation is pretty much universal in western countries - the UN is at the moment working on a globally harmonised system of hazardous substances management.
Thinks2much - From the MSDS you can see what the offending compound(s) are likely to be. It will at least make you slightly less ignorant.