Patchy areas of hairloss and pustules indicate a skin infection. The infection can be due to bacteria, demodex (Mange), or ringworm (fungal skin infection). Pit bulls are prone to allergies to grass, pollen, and even foods, and they commonly develop bacterial skin infections secondary to the underlying allergy. I recommend taking your new dog to your veterinarian for a thorough physical exam, vaccinations, fecal exam for parasites and blood test for heartworms, and getting him on a monthly heartworm preventative. At the same time, the veterinarian will be able to perform skin scrapings for microscopic analysis to identify the type of skin infection present in your dog, and then prescribe appropriate medication to treat the infection.
also the spot of thinning hair do not look red or swollen just like his hairs falling out i looked up pics of mange and they all look red and nasty he dosn't look this way
also hes fixed not sure if that helps