My LO had/has it. I give him Rx medicine 3x a day.
I also think he now has a yeast rash on his butt -- I'm on antibiotics for c-section (maybe passed to him through breast milk?) & his thrush may also have contributed to the rash. For his butt, I'm using an OTC anti-yeast/anit-fungal cream.
I also have a Rx cream I use on my nipples after each feeding/pumping session.
His mouth seems to have cleared up, and I just started trying to clear his butt rash.