Black henna contains high levels of a chemical called paraphenylenediamine (PPD). PPD is the stuff found in some hair dyes, but it is in much higher concentrations in black henna.
PPD is allowed for restricted use in hair dye, but its use for skin contact products such as temporary tattoos is illegal in the European Union.
The chemical is usually used in hair dyes, and not in brown or other coloured henna.
The para-phenylenediamine in black henna can cause blistering of the skin, painful burns and can lead to scarring.
It can also cause the sufferer to have a lifelong sensitivity to para-phenylenediamine, increasing the risk of severe allergic reaction when using hair dyes in the future.
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