If you live in an area that's fairly warm right now, your dog can get fly bites that can appear as red circles. If this came on suddenly, right after being outside, and they fade quickly, it might just be that.
But do take your dog to the vet and get his shots. Its your responsibility. In most areas, its the law, at least to get rabies shots. Do the right thing.
Usually when we see a dog with allergies under 1 year of age it's usually food related. The only true way to tell is to do a strict! elimination diet byt putting the dog on a limited protein source food like Nature's recipe venison/potato, fish/pot or vegetarian formula. Then they are fed this food exclusively for about 8-10 weeks to get a true sense if the diet is working. During this time NO TREATS! Nothing but the food. Your can use extra kibble for a treat or carrots, banana, marshmallow or canned pumpkin are good too because they don't interfere. The problem is your pup could be showing signs of bacterial infection of the skin which is the common problem of allergies. Either way your dog needs his regular vaccines too allergies should be the least of your worry because he could be exposed to something more dangerous and contagious for your kids as well. We see a lot of Pits in our clinic all the time with allergies but proper overall healthcare is necessary! Please read any of my earlier posts about managing allergies and my tips on buying meds and keeping the vet bills down. Good luck and please be a responsible pet owner and get your pup his vaccines!
a friend of mine..here girl had the same thing and found out later she was alergic to chicken in the dog food..good luck