Some hennas may contain ppd or other oxidative dyes. If you’ve had any kind of allergy to any haircolorant please talk to your physician before trying something new ( even EcoColors ) because even though EcoColors is ppd free, there are other oxidative dyes present that could have a cross reaction to your allergy and could cause an allergic response. Allergies aren’t to be taken lightly and could be fatal! Don’t take a chance.