Yeast is a tiny, microscopic fungus that's all around you, on you, and even in you. For the most part, it does more good than bad. It's an important ingredient in bread and beer, for example. And in low amounts, it exists harmoniously with other microorganisms in your body, mouth, and throat. Infections only occur when something causes the yeast somewhere in your body to multiply. If you think you have a yeast infection in your mouth or throat, we'll let you know what may have caused it, symptoms you should look for, and what you can expect from diagnosis and treatment when you visit your dental or health professional.