Info on henna and indigo found on:
www.mehandi.com
Henna is a plant which has a red-orange dye molecule and works in a mildly acidic mix. Indigo is a plant that has a dark blue dye molecule and works in a mildly base mix. If you dye white hair with henna, you'll get a coppery red. If you combine henna and indigo in the same mix, it will dye your hair a brunette color. If you dye your hair first with henna, rinse it out and immediately dye over that with indigo, you'll get beautiful black results!
PPD (Para-phenylenylendiamine) is the main allergen identified in allergic reactions to decorative skin paintings. Para-phenylenediamine is a colourless/slightly pink, grey or yellow crystalline solid (lumps or powder). On oxidation, usually through exposure to air, it turns red, brown then finally black. PPD is essentially a dye and chemical intermediate. It may also have been found in textile or fur dyes, dark coloured cosmetics, temporary tattoos, photographic developer and lithography plates, photocopying and printing inks, black rubber, oils, greases and gasoline. PPD is a low toxicity diamine used as a component of engineering polymers and composites, aramid fibers, hair dyes, rubber chemicals, textile dyes and pigments. PPD is selected for the outstanding properties it imparts, including high temperature stability, high strength, and chemical and electrical resistance.
Henna gives an orange/reddish-brown stain. Any product that calls itself black henna must contain an ingredient in addition to pure henna to achieve its ebony color. In most cases, this added ingredient is PPD, that is also found in many black hair dyes. Another reason for using PPD additives is to speed up the tattooing process. While traditional henna staining takes 2-12 hours, a pure black tattoo can be achieved within an hour or two with the addition of PPD, and there will be a longer lasting effect as well. "
"The findings of a mass spectrometry analysis of commercial black henna performed by Chung et al. demonstrated a major peak at the mass-charge ratio of 108.1, which corresponds exactly to the molecular weight of PPD. There was no line at the molecular weight 174.2, that of the active agent of pure henna. This was the first sophisticated, scientific proof of what almost every tattoo artist or supplier had known for years.
In other words, there is no such plant as or plant that gives black henna and here we see scientific proof that it is the chemical called PPD that makes this phenomenon. Its nothing to do with henna at all, other than a piggyback ride from a legitimate and healthy art form turned into a marketable and highly profitable scheme that harms people. Luckily, there are people speaking out on this to make the people who manufacture, sell and use PPD to be held liable for what they are doing.
An important factor to remember about PPD is that it is cheap.
What happens to people who use it?
The CDC lists p-Phenylenediamines as being known as one of many contact allergens. The NIOSH Pocket Guide to Chemical Hazards lists exposure routes as through inhalation, skin absorption, ingestion, skin and/or eye contact. Symptoms listed are: Irritation pharynx, larynx; bronchial asthma; sensitization dermatitis.
There seems to be a small misconception that you will react immediately to PPD, so if it doesnt burn/sting or otherwise present an effect immediately, one is safe from any reaction. This is not true and its a dangerous myth! PPD is known for its short sensitization period- that means you might not get or see an immediate reaction, but the next time you get a black henna tattoo or otherwise come in contact with PPD you could have an extremely bad reaction. PPD elicits not only contact hypersensitivity but immediate-type hypersensitivity.
Not only that, but the sensitization issue seems to be much larger for another little known reason: Subjects have been shown to react to lower concentrations of metabolic breakdown products of PPD than to the actual PPD molecule itself. In the simplest terms, this means that PPD breaks down in your body in a sort of digestive process. These smaller amounts are more sensitizing than the actual PPD is when it first comes in contact with you! Thats probably a notable factor in the sensitizing issue. As it breaks down, it is, in effect, stronger and more likely to cause cross sensitizations with other products, including but not limited to PABA based sunscreen that people wishing to prevent skin cancer often use.
Thanks.
Good luck!