Health effects
Though user accounts cite few, if any, negative effects of natural henna paste, pre-mixed henna body art pastes may have ingredients added to darken stain, or to alter stain color. The health risks involved in pre-mixed paste can be signficant. The FDA considers these to be adulterants and therefore illegal for use on skin.[20] Some pastes have been found to include: silver nitrate, carmine, pyrogallol, disperse orange dye, and chromium. These have been found to cause allergic reactions, chronic inflammatory reactions, or late-onset allergic reactions to hairdressing products and textile dyes.
• Medical report of heavy metals such as nickel, cobalt, chromium, lead and mercury found in henna tattoos [21]
• Allergies Associated with Body Piercing and Tattoos[22]
• OSHA on silver nitrate[23]
• CDC on silver nitrate
source:Wikipedia
