Henna tattoos are a popular body decoration for children and adults alike. Artists often host booths at fairs where children can step in and get anything from a butterfly to Chinese symbols emblazoned on their body parts. Kits for home use are available at specialty stores and are fairly simple to use. The advantage of henna tattoos is that they offer a temporary bit of tattoo glamor, are painless and wash off within two weeks. The main ingredient in henna is hydroxynaphthaquinone which is obtained from leaves of the Lawsonia tree. Hydroxynaphthaquinone alone is not carcinogenic, but when combined with para-phenylenediamine (PPD) the mixture has been documented as causing problems. PPD is a synthetic dye used to accelerate the drying time of the henna mixture, darkens the overall tattoo and allows for more precise, detailed images.The chemical has been documented to cause severe blisters, skin rashes and scars. In 1979 the US National Cancer Institute labeled PPD as a possible carcinogen due to a high incidence of liver cancer in workers at PPD production plants. Not all henna artists or henna kits use dye with PPD, if the resulting tattoo is an intense dark black and lasts for more than several weeks, it likely contains the undesired ingredient.