Henna comes in powdered form. If this powder is stale, it will never give a good and longer-lasting color to your skin or hair. To save yourself from disappointment always shop for pure henna from a well reputed company.
Your skin might not give an abrupt reaction to box dyes or metallic salts but it is definitely harmful. I can tell you on thing for sure, no matter how pretty the color is it is never worth risking your skin or health.