Yeast (candida) is a normal part of the digestive Flora and, in a healty dog or person, is kept 'under control' by a strong proliferation of the beneficial bacteria. Your dog will have a yeast problem when the necessary bacteria is destroyed by outside factors, most frequently vaccination reactions. That same bacteria, when present in healthy amounts, also accounts for as much as 70% of immune function; therefore, its destruction can desimate much of immune system capabilities.
There are multiple underlying causes for dog skin sores including parasites (fleas, mites), poor grooming, dog skin infection (bacterial pyoderma, fungal), endocrine diseases, skin or hair follicle disorders disorders such as seborrhea, medication side effects (from corticosteroids) and allergy.
There are various diseases that causes eruption of blisters on the skin tissues such as: 1  Erythema multiforme is what causes blisters on hands and palm, sole of feet, mouth, genitals and other parts of the body. The blisters may also be accompanied with other symptoms such as fever, muscle aches and sore throats.