They’re commonly known as hot spots, but the medical term for those bare, inflamed, red areas you often see on dogs is acute moist dermatitis -- a bacterial skin infection. Anything that irritates your dog's skin enough to make him scratch or chew can lead to the pain and itch of hot spots, which, if left untreated, can quickly grow larger.
A hot spot's location can help your vet diagnose its cause. Fleas, for example, may be the source of a hip hot spot, while a hot spot at the ear might point to ear problems.
Treating hot spots may involve shaving and cleaning the irritated area, antibiotics, anti-inflammatory drugs (NSAIDS), steroids, or topical medications, depending on how bad the hot spots are, and how much pain your pooch is in.