There is another fly in the horse fly type, but folds it's wings flat, called a Cleg (+g? ).
Ivery been bitten a few times on my arms or legs, can turn very nasty, ended up at A&European a few times +ABs. Dr advises Piriton tablets, I always keep some in and start taking as soon as little lump starts looking like a swollen reddish patch.
Last time hospital doctor drew a line round it (most of my arm by then), said if it went beyond that, I had a red line , or started to feel confused I'd to get back there without delay, they'd wanted to keep me in on a drip but I wanted to go home.
Scary.
Get to doctor or Hospital if you feel it's getting worrying.