It does damage your hair, a bit more every time. You can try a type of shampoo that has bleach infused in it.
It's a healthier way of bleaching your hair.
I also recommend Jerome Russell's hair dye.
It is as close to permanent as I've ever used before. Didn't fade for months.
It only began fading once I started using a toner, to take out the colour, and even then, it was still strong.