Although we may think that the body lives alone, it actually shares itself with many organisms including yeasts. The type that’s most common in dogs is called Malassezia and it exists happily on skin without causing a problem unless something happens to create havoc, giving the yeast the opportunity to overgrow. For example, an allergic flare-up is a fairly common cause. An allergy to what though? It could be to a food, or something in the environment. It can also be due to a hormone imbalance, or an immune deficiency (veterinarians can test for this) and if the dog happens to have excessive oil production of the skin (seborrhea), s/he is predisposed to yeast overgrowth to begin with. So, how do you know the problem is yeast? Read more Smelly, Itchy Dogs: Can It Be a Yeast Infection?