If you get stung by a bee one of the first things you need to do is get the little stinger out. An efficient way to do this is to cut a fresh onion in half and rub it over the stinger, it will draw it out.
As a kid I was highly allergic to bee stings (almost died once, ended up in hospital in a bad way when I got stung on the thumb) - if the stinger stays in the swelling/pain will continue on.