itchy redness

oh the itching if it only would stop but no this stupid rash keeps spreading. I think I have had an allergic reaction to something I have eaten or touched in the last 2 days. I have a rash all over and it just is getting worse. It started on my belly and has spread now my face and head itch and my face is a big red blob. Oh I just wish this would go away. I took benadryl but it is not helping.