I was told last week my newborn son thrush. his dr. prescribed nystatin which he was supposed to have for a week but it's gotten worse. why is that?

R U using it right ?: Nystatin works by killing the yeast on contact. If swallowed as it is given, it helps nothing.You can use the med like a paint by taking a q-tip and soaking the pad before touching the whitish areas in the mouth. If the kid were old enough to swish & swallow, that would help, but most infants require some direct applications.