PPDA is used for almost all hair colors.
It turns dark when it is oxidizied.
This is the reason why it is used in many hair colors.
However as some clients are allergic to PPDA, once a person gets allergic, it is quit permanent.
We use Henna or Hair-Manicure which doesn’t apply on a scalp derectly for clients who are
allergic to PPDA.
Recently we found PPDA-Free alkaline color and PPDA-Free Herb Color which is organic.
There aren’t large valuations of colors but you don’t have to worry about PPDA and allergies.