Hot spots are basically a skin staph infection. It could be a scratch or bug bite that starts one. Moisture seems to keep it going so drying out the area helps. I typically wash the area with a anti-bacterial soap and then spray with Vetricyn. Let it dry or dry with hair dryer to speed up process, and then put Gold Bond Medicated Powder on it. This works if you catch it early. Also have used Neo Predif from the vet and that works well. Do this a few times per day.
Are you looking for a minimum or maximum age to neuter a dog?
