Same here, I only noticed it because I was doing someone elses hair with a different brand so actually read the instructions for a change, and I thought it was really strange!
Oddly enough my tattoos did temporarily go all bumpy when I had an allergic reaction to an antibiotic, although I'm sure they weren't the reason for the reaction!
some of the 'temporary' tattoos that you can get on holiday contain a chemical to stain the skin and it is this chemical that is also included in home hair colourant, you may or may not have had a reaction to the tattoo, but your body will have noticed it and then if you use a home hair colourant which also has the same chemical your body could decide to fight against it and it is this that causes the severe reactions seen in newspapers and on tv. Sorry I probably haven't explained this very well, but was trying not to get too scientific. See here for more details www.womenshair.info/articles/article6.htm