Practical non medical advice here, my wife owns a tattoo shop. In our experience with both of us being allergic to a lot of environmental things, you’re not likely allergic to the ink itself (that has a very ugly and very noticeable look) but probably having a general inflammation response from something else. Like being allergic to cats or dust. That kinda thing.

Different inks also use different ingredients to keep the pigment stable. Some use plastic, some use tree resin, some don’t use anything. Anecdotally those carriers do keep the lines looking significantly sharper over 5-10 years.

Last on the ink grain - totally possible, especially if it had a plastic carrier. My wife has very thin skin on her hands and the black ink on her knuckles caused her some pain with pressure. So she cut it open with an xactco, and managed to squeeze out a nice lil piece of black plastic. Kinda freaky eh?

The raised itchy lines are very common though. I don’t know if anyone with significant coverage that doesn’t have the issue. It can also be confused for scarring - especially on the lines where people are more heavy handed - the raised pieces can be scar tissue. If you were to get it lasered you would still have raised, scar colored lines left behind.