I have read that body tattoos when performed in volume, placed deep in the dermis, can migrate and develop embolisms to the brain and other organs, in this case the eye.  I have discussed some of this in my article: https://newhair.com/wp-content/uploads/2018/11/Journal-of-clinical-and-aesthetic-surgery-Article.pdf.  Most of the inks used by the tattoo industry have insolvable material, heavy metals and these particles can be moved into the lymphatics of the skin where they get transported to the venous system, into the heart and then pumped almost anywhere blood goes. I don’t believe this is a significant problem for SMP; however it is a real risk for those in the population who have extensive tattooing.  The more the tattoos, the greater the risks.
We use only organic pigments that are placed at the very upper part of the dermis as shown in my recent post on baldingblog:  https://newhair.com/baldingblog/smp-scalp-micropigmentation-alopecia-areata-can-activate-disease/. I don’t believe that any of the complications that are reported by me and others. I believe what we use is relatively safe be cause of our use of the organic pigments in the superficial dermis with Scalpmicroigmentation.

https://jamanetwork.com/journals/jama/fullarticle/2723634