
I've had one once on one of my Collies, from a red ant bite. On advice from other breeders, I clipped the fur away a bit, cleaned it and then used antiseptic powder (dries it out, don't fancy the cream) and it was clear in no time.
M.
Edited to add, the powder seems to soothe it, and she was fine without a buster collar, but this may be a dog by dog case LOL.