J.P.
Thrush is a form of Candida in the mouth, nipples, etc or yeast overgrowth. I find that many people get an overgrowth from food choices (sugar, dairy mushrooms, breads, etc.) or antibiotics.
Many women get reoccurring yeast infections transmitted from their husbands, etc. Babies and moms can keep transmitting it through breastfeeding....very often caused by antibiotics given to mom and/or baby at the hospital.
I find that PB8, ThreeLac, etc., (with diet changes) can get rid of it. Oregano capsules with 70% carvacol works even better. Some people have used gentian violet for it.