I have had the same reaction to blues in a few of my tats. They look as though they're blistering...and I'm talking YEARS after getting the tattoo...it goes away...usually only happens once...I think it was the ink itself that i had a reaction too...I do recall it happening with some pink shading of one teeny bit of another tattoo...

I read, during researching this, that the metals in the dyes might be to blame. There is some blistering if I don't leave it alone. Any tattoo artists have ideas to ensure this won't happen again, know brands of ink that this doesn't happen with? help...

This also occurs as a histamine reaction. I have that problem with the teal in my tattoos. I do not have metal allergies but I do get heat rashes and it might be a reaction to foods that I have consumed at the same time. Usually only lasts for a short while but there is not blistering that occurs just it raising.

I understand this is fairly common with reds and blues that reactions can occur. Black cherry did not do well on me in some areas but in others it is a beautiful color, so it might depend on where on the body the ink is. The teal I have is universal in its raising, but it doesn't do it all at the same time, just areas might raise or a specific tattoo and not another.

Just a person's body chemistry at that moment in time maybe too. :)

So, just be aware and make sure the tattoo artist is knowledgeable about their inks. :)

It's worth asking the artist who did it what brand of ink they used, as you may be able to find the active pigments & sneaky sneaky with another brand of colour if possible.
Once your system has reacted in situ it is permanent sensitisation and tends to be slowly increasing over time. Sun and other chemical exposures tend to increase it. By the way many of the actives in hair dyes are similar pigments so beware if you colour your hair.