dry bald sores

Cora, your dog may be having an allergic reaction to something causing the bald patches.  Allergies can be from food or something they inhale, come in contact with or flea bites.  On occasion dogs can get ringworm which causes hair loss in patches.  I would encourage you to take your dog in to the vet because the problem will most likely not resolve itself unless you know what is the cause and what to do.