yeast is caused by a lowerd immune system or carbs ,all dogs have healthy yeast but when a dog gets poorly,stressed ,anxious,then the yeast multiplies and becomes overgrown,then the symptoms start,paw licking,smelly,sore ears usually with brownish discharge,reddening of the fur,itching ,antibiotic and other meds cause the good bacteria in the gut to die off then this in turn affects the immune system hence yeast,karen