I get big welts like that with any bug bite, including plain old mosquitoes. It's one of the reasons I hate camping. If a bunch of us are sitting around the camp fire, I'm the only one getting bitten.
My horse used to be allergic to bites from deer flies and horse flies, they would swell into large welts all over his body.
The vet prescribed daily antihistamines.....but for hubby it'll be cheaper to slap on some onion!!
Today it looks the same size, maybe a tiny bit darker. Not much of a change. No itch.
After he got bitten, he had a bump there, then later in the day he slipped on our stairs and fell. He used his elbows to brace himself from falling further, so maybe the bruise just "happens" to be in the same spot? Strange.
Fortunately we have a town doctor who works tonight, we'll see how it goes.
Thanks for all your replies!