What are "Hot Spots" and what causes them? Technically this skin problem is called a deep pyoderma or infection of the skin. It can have several causes such as skin trauma from scratching, allergies to seasonal pollens, food allergy, flea allergy, insect stings etc...
Treatment includes treating the underlying disease, skin inflammation and the infection with antibiotics.
These are painful infections. The wounds must be clipped to remove hair that will stick to the wound. Cleansing to remove debris, air to help the wound to "breathe". Preventing them from licking and chewing at the wound is very important so E-Collars may be required to block them from getting to the wound.
It can take up to 3-4 weeks of treatment to heal them and they are susceptible to developing new ones in different areas if the underlying problem is not treated.