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.
By Mayo Clinic Staff. The precise cause of canker sores remains unclear, though researchers suspect that a combination of factors contributes to outbreaks, even in the same person.Possible triggers for canker sores include: 1  A minor injury to your mouth from dental work, overzealous brushing, sports mishaps or an accidental cheek bite. Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. 2  Behcet's disease, a rare disorder that causes inflammation throughout the body, including the mouth. 3  A faulty immune system that attacks healthy cells in your mouth instead of pathogens, such as viruses and bacteria.