Incubation period for adult oral yeast infection?

Not quite that way: Oral yeast is usually the plain old candida. We get it when we are babies, and we always have it. Everybody has it. When a person gets overgrowth of it (called thrush), it is generally due to something else going on inside the person, such as another medical illness, or a medication side effect. For example, asthma inhalers like flovent, that have steroids in them, can cause oral thrush.