My wife was looking at the box last night and said she wants to try it soon. We'll see what that means.
We did start looking into the process in more detail, and apparently they practically beg you to perform a spot test on your arm before you commit to your hair each and every time! They say that even if you've dyed your hair with their product repeated with no issue in the past, it's still possible for a skin allergy to develop at any time.
Oh, and they even have instructions in English and Chinese online if you scan their Q-Code. We didn't look at them, but it's nice to know.