What causes and how is thrush treated? symptoms? could pacifier cause this?

Yeast Infection: Thrush is caused by a yeast called candidas & can be treated with an antifungal prescribed by a doctor. If bottle fed, there's fungus on the nipples so boil nipples and pacifiers daily. If breast fed, you need to treat the mom too. Normally, the bacteria that live in our mouths stops the yeast from growing, but in babies it's not well established enough to stop the yeast yet.

Yeast: Thrush is a yeast infection in the mouth, generally in young babies in the first few months. There's white plaques on the inside of the lips, on the tongue, the sides of the mouth, and the roof. The difference between this and milk residue is the thrush doesn't brush or rinse off. It's treated with oral nystatin, an antifungal solution painted on. The pacifier can pass the yeast around.