Qualcuno può aiutarmi?

I am a vet. I’d say with a very high degree of confidence that they are hot spots. It’s a superficial infection. Also called acute moist dermatitis. Nearly always they heal within a few days with some antibiotic cream like fucidin/fucicort (the latter has a steroid component which might make the redness go down faster but it’s more limited in how many days it can be used, however it should have cleared up by that time frame anyway). It’s one of those things that look nastier than what they actually are. They usually just appear out of the blue. Most dogs will get it a couple of times in their lives.