I know when I was a kid, my mother would make a paste of a little meat tenderizer and water. If you put it on right away, it really does help. Just leave it until it dries and then brush it off.
DD gets huge hives from mosquito bites, but I never have any meat tenderizer.
She usually gets some relief from putting an ice cube on it for a few minutes, but that might be hard with so many bites! Sorry you're miserable!!
Ooooh yes, just saw Krasota's post. DD did that when we were at the Ozark Folk Center - one of the docents showed her which leaves and how to do it. She didn't hive up from the bites she put it on!