I would presume the ink is not good, to go into One's blood stream. I cannot answer the reality of it though. Simply because if One chooses not to see that the ink is bad for Oneself, it most likely will not be. Although, I have not paid attention to that aspect.
I got a tattoo around my ankle about 8 years ago. My son has had several tattoos put on him in the last year. It has not caused any dis-eases for him or the one for me did not either.
I am sure if you look at the energetic viewpoint that would be much different than the physical one. Energetically a needle with a 'foreign' substance is being injected into different meridans. This creates a congestion (if you will) of the energy (chi, prana) flow.
I do not know if this helped you or not. I hope you can use something from it though.