| Products sold as "black henna" or "neutral henna" are not made from true henna, but may be derived from indigo or cassia, and may contain unlisted dyes and chemicals. You run the risk of contact dermatitis as what they are calling "henna" is probably PPD. I have posted on this before in this forum. Do a Google. Concentrations of p-phenylenediamine (PPD) found in the "black henna" paste studied at the NYU School of Medicine this past summer contained nearly ten times the amount allowed in hair dye.
http://en.wikipedia.org/wiki/Henna http://www.cbc.ca/consumers/market/files/health/henna/ http://www.hennatribe.com/ppd.php http://www.expat.or.id/medical/blackhennareactions.html http://www.expat.or.id/medical/blackhennareactions.html http://www.hennaforhair.com/ppd/ppdreaction/ Henna is a plant that can only produce an orange dye. If you saw "black henna" being sold they are trying to fool you. | 
