Gentian violet is to be used by applying it to the nipple and as the baby nurses he will get his share of gentian violet, it will turn his mouth purple and your nipple too but its supossed to help. I don't know about giving it to him directly, it might irritate his little stomach because he would be ingesting more than if he gets it from your nipple.
My son had to take the nystatin for like 10 days before we saw any relief. I also had to apply it to my nipples as well to make sure we weren't passing the infection back and forth. Thrush can be very difficult to treat...be consistent with the medication and if after a week + you still don't see any relief, they do make diflucan in an oral suspension that babies can take. Diflucan is a stronger yeast killer. Good luck and fingers crossed you don't get it because I did and it was sooo painful! The nystatin didn't work for me, I had to get diflucan and I've been on it for like 4 weeks! Still have one more pill to take this week!
It does take a while for it to take affect, my son had it. Watch for a diaper rash, they can get them with thrush. But the Nystatin made it go away for my son. The spitting up could just be cause he's only three weeks old.
My daughter had thrush when she was a newborn as well, and dr. also prescribed Nystatin. It worked, but took a while. I also had to apply some topically to my bbs, because I was breastfeeding. You can keep passing it back and forth!
-1st