It is possible, by using rare pigments, and lengthy enchanting procedures, for an individual to be inscribed with an enchanted tattoo. While this might seem extremely advantageous, it does have its share of pros and cons, as are outlined here:
Advantages
1) Can't be misplaced.
2) Can't be stolen.
3) Can't be casually broken.
4) Could easily be placed somewhere not normally visible.
Disadvantages
1) Current magical theory doesn't allow you to put more than one enchantment on an object. This applies to putting magical tattoos on people as well.
2) It is not possible to ditch the old tattoo for a new one. Even after an enchanted item has been permanently disenchanted, it still has enough of a magical aura to make it unsuitable for re-enchanting. Better choose your tattoo wisely, because you won't get a second chance.
3) Nontransferable. If you've got the Pennywhistle for Summoning Friendly Aeroplasms, you can loan it out to your friends if they really need it, you can sell it for quick cash, you can stash it for safekeeping, your pals can borrow it and use it to save your butt while you're out cold, etc. Magical tattoos aren't usable by anyone other than yourself (no matter how much you might wish otherwise).
4) Getting an enchanted tattoo is "extremely" inconvenient.
5) You, personally, would detect as magic.