Help—advice needed. What is this rash?

Just got a new tattoo (pic 1) 24 hours ago. Didn’t use second skin as I have reacted badly to it in the past, so artist used cling film/saran wrap instead and told me to keep it on for 4 hours until I shower that night (I finished my tattoo quite late at around 11pm last night). She also told me to wrap the new tattoo in cling film after the shower just to protect it while I sleep so that the sheets/clothes don’t get dirty etc. I did that. Slept for over 12 hours and took off the cling film this afternoon. A couple hours ago this rash (pic 2 &3) appeared. Weirdly enough it’s only in the places where I don’t have any tattoos. It also doesn’t feel itchy, hot or even warm to the touch, and when I touch it I can barely feel its raised (it looks very raised in the photos because I guess lighting).

Anyone have any idea what this is? I’m planning to take an antihistamine tablet to see if it helps.