So-called 'black henna' is not henna at all, but often a dangerous chemical called PPD (para-phenylendiamine) - a black coal tar dye (aromatic amine) which is known to cause permanent scarring, bladder cancer, liver problems, kidney failure, even death. Smokers are even more at risk for serious diseases if they regularly are in contact with PPD, and since PPD is present in most commercial hair dyes, people who dye their hair are also sensitized through repeated contact.
Other mixtures include real henna mixed with PPD, gasoline/petrol, kerosene, or other toxic substances - all of which are capable of entering the blood stream and causing long lasting harm. PPD in particular builds up in the liver and creates sensitization - you may not react the first, or the tenth time, but with increased contact with this harmful chemical you will become sensitized to hair dye, some sunscreens, black clothing, and can suffer serious health damage. Remember, PPD reactions are NOT 'just' allergic reactions, but a form of toxic shock - much more dangerous.
Thus, it is important to be cautious about ALL forms of temporary body art - not just on vacation in India, North Africa, or the Middle East, but also here in Europe. I have heard reports of such products in Turkey, Poland, and Italy, for example, and, unfortunately, many are sold here in Germany on seemingly reputable internet sites.
Many so-called 'artists' choose the cheap and toxic way of making money fast and offer quick staining 'black henna' or other questionable mixes. One reliable indicator that PPD is being used is that the result is instant - PPD stains (and sometimes permanently scars, see link below) immediately. Real henna requires several hours, even days, for the stain to develop, and the artist will tell you you must leave the paste on the skin as long as possible.
A henna artist should ALWAYS be able to tell you what is in her paste! If she cannot, she is risking her own as well as your health!
The same goes for ready-mixed products such as pre-mixed henna cones, even if they don't directly stain black (for example 'Golecha') - many of these do contain small amounts of PPD and/or other dangerous chemicals - better to be safe than sorry. The fact is that real henna has a short shelf life, so anything sitting around on a shelf that still stains the skin MUST contain some other ingredient, and is therefore - at the very least - mislabelled when it is sold as henna.
I NEVER, ever use any form of black or chemical henna and STRONGLY advise my clients to avoid it and help educate others that REAL henna always stains reddish brown, and requires time for the color to develop. Any pictures of my work where the design looks black are pictures of the paste still on the skin.
More information on the difference between natural and so-called ' black henna' here:
Please help spread the word that REAL henna stains red-brown and needs time to develop. Quick-dye products or products that stain black are most likely dangerous to your health (and the artist's as well!) - Inform yourself and your friends, and protect your health!