I have a solid black cross tattoo on my arm that was done about a year ago without any problems. And ever since its been healed, different areas of the tattoo would become slightly raised and itchy. When it first happened I thought that I may have just been bitten by a mosquito on my tattoo, but the swelling is in the shape of my tattoo, and it keeps occurring and going away every couple of months.

Any idea why it's doing this? :/