Allergic Reaction

I’ve had this tattoo for over a year, but every now and then since I’ve gotten it, it gets really itchy and red in the surrounding area. I’ve always chalked it up to a bug bite on the area but now some parts of the ink feel ‘lifted’ or swollen or however you want to describe it. I have other tattoos that don’t itch or get ‘lifted’ but none are filled or as thick as this. Any ideas?