In the warm climate of the Middle East, the heena plant, which has the scientific name Lawsonia inernis, grows beautifully. Over the centuries, inhabitants of the countries in the Middle East have learned how to crush the henna leaves, and to thus produce a powder. If that powder is mixed with mehndi oil, it can be applied to the skin.
Why would someone want to put a mixture of oil and powder on the skin? Well, that powder happens to contain chemicals called tannins. Those tannins give the powder from the crushed leaves the ability to stain objects touched by the powder. When mixed with mehndi oil, the powder can stain skin. The skin becomes one of various shades of brown.
The Egyptians used to rub henna and mehndi oil on the fingers of deceased Pharaohs, before beginning the process of mummification. Later, various cultures encouraged the creation of henna/mehdhi tattoos. Each culture had its own unique type of henna/mehndi tattoo.
Arabs chose to put large flowery designs on their hands and feet. Indians preferred to make fine lines in each henna/mehndi tattoo. They painted their hands, forearms, feet and shins with lacy henna/mehndi designs.
As the inhabitants of the Middle East began to trade with Europeans, the stain created by henna powder became familiar to some Europeans. Then as other Europeans traveled to all four corners of the globe, those traveling Europeans, some of whom had become familiar with the henna/mehndi designs, met Polynesians who wore a darker and more permanent skin design—a tattoo. That meeting paved the way for creation of the henna/mehndi tattoo.
Although the Polynesian-style tattoo last much longer than the henna/mehndi tattoo, not every person wants to have a permanent design on his or her skin. Many people like to have the ability to remove a tattoo, much like a woman can remove make-up. Those people are eager to purchase the henna/mehndi tattoo kits, kits available at various sites on the Internet.
Such kits include stencils, design books, transfer tattoos, bindis and faux body jewelry. They allow a person to put a blue or black tattoo on any part of his or her body. Such a tattoo remains on the skin for one to four weeks.
The makers of the henna/mehndi tattoo have sought to capitalize on the familiarity of hair dyes with henna. In the United States, the FDA has recognized the safety of such hair dyes. The FDA has not, however, given a nod of approval to the selling of henna/mehndi tattoos.
The original skin stains made by the henna/mehndi mixture were either brown, orange brown or reddish brown. Such stains contained only the chemicals in the henna plant, plus the chemicals in mehndi oil. The blue and black tattoos created from the henna/mehndi kits have additional chemicals.
One of those chemicals is coal tar. The scientific name for coal tar is p-phenylenediamine (PPD). The FDA has found that many people are allergic to PPD. That finding has forced the FDA to seek restrictions on the importation of henna/mehndi, skin staining products.