Can I use this Iranian henna to lighten my dark hair or cover grey completely with a black color?

It is important to understand that this product contains pure Lawsonia inermis leaf powder, which works by staining the hair shaft rather than chemically altering it. Because henna binds to the keratin on the outer part of the hair, it cannot lift or lighten your natural pigment. If you have dark hair, you will not see a significant color change, though you may notice richer, warmer reflections in sunlight. For grey hair, the result is typically a vivid warm copper or orange tone, not a neutral or dark shade. If your goal is to cover greys with a black or dark brown color, this single-ingredient formula will not achieve that. To get darker shades like brown or black, henna is traditionally paired with other plant powders such as indigo or basma in a second step. Always perform a strand test on a small section of hair first, as the final result depends heavily on your starting shade and hair porosity.