Henna is derived from lawsonia inermis plant leaves and is commonly used for dying hair, and skin. Black henna, used to dye the hair black rather than red, can be made by adding indigo dyes or heavy metal salts. The heavy metals commonly added to darken the henna are lead acetate, silver nitrate, and/or copper acetate.  Knowing that the amount of metal salts in hair dyes is regulated by the FDA, hair samples were tested for the presence of heavy metals on dyed hair, using a wet chemical test. Testing revealed that hair treated with henna, or black henna, from the USA and a metal solution showed no positive test.  A sample of black henna from India possibly showed a positive test for lead acetate only.  Atomic Absorption Spectroscopy (AAS) tests will be performed to see if the metal was actually absorbed by the hair.

Qualitative and quantitative analysis of heavy metals in hair dye henna

247th National Meeting (2014)

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