I know I've posted this before, but considering this is a "bee" thread, I'm going to repeat it. About 20 years ago, my Dad was staying with us; he was getting feeble and needed care. He liked to sit on our patio and just take in the out doors, especially if someone was working in the yard. On this particular day, I was mowing. We have a power pole not too far from the patio, and there was a Rose of Sharon at the base of the pole, in full bloom. I made a couple passes around the pole with the mower, knocking some of the blooms off and a couple landed in my lap.
I brushed the blooms out of my lap, and unfortunately one contained a bumble bee that stung me square in the palm of my hand. That was the most painful sting I have ever received. Seemed like I could feel it all the way to my ear. My Dad saw what happened; and when I got off the mower, he said "If you will put a drop of onion juice on that it will kill the pain". I thought that was the most ridiculous thing I had ever heard, but I told him that would try it, figuring a couple ibuprophen would be as good as it gets. So, I got an onion, stabbed it with a knife, and put the juice on the sting. The results were almost immediate; it quit hurting completely. I was simply amazed that it worked and worked so well. I have used it a couple times since, and it has always worked.
Now it doesn't reduce the swelling, or at least any that I could tell, but what it did was enough.