tattoos

[Niccy Scholfield]

We were wondering just exactly how tattoos work. Unlike a protein dye that 
comes off when the skin sloughs off, a tattoo is guaranteed for 99 years! 
We figure it must be a protein dye of sorts, but which cells/structures does 
it dye, do any cells die, and how come cell division doesn't make the tattoo 
get bigger and bigger, or dilute out?  If the skin is a fluid organ, how can 
a tattoo stay static for decades???  Is the basement membrane involved?  
What dyes (other than amido black) are commonly used and what do they 
contain? If the process kills/fixes cells, why aren't they replaced or 
removed by phagocytes?
We realise that this is quite a hectic question, but any contributions that 
will allow us to put sleepless nights behind us will be much appreciated.

Niccy and Linda.