Does anyone know if it's safe to take antihistamines??

I am going crazy with this itchy belly. I can't use moitsurisers (even olive oil!) because I come out in a rash that's even worse!!!

Have been in the shower for the last 20 minutes trying to soothe it down, which works, but as soon as I get out, it's back itchy again!!!

Anyone got a good distraction/remedy?