When I think back, my son had recurring thrush from the get go and my guess is that it was a result of MY being put on heavy Antibiotics after his birth while I was breastfeeding.
As he got older, I always thought that his cracked lip corners were a side effect of his recurring strep ... but now I wonder if the increased bacteria played the bigger part. Which came first, the strep or the angular cheilitis? Are they related? His symptoms of strep have always been atypical and he never seems to get a sore throat or fever with it. Only a swab culture can diagnose it for him. Whenever he was placed on Antibiotics it seemed that they would work for his throat and lips and I had him eat more yogurt than usual during those times. It seems like a misunderstood and vicious circle. His doctor feels that he simply has chapped lips and the dentist hasn't offered any input.
Update: My son did the treatment twice the first day and hasn't since. I changed his toothpaste (this new outbreak did come at a time when he switched toothpastes to a 'complete' type) as well. He is sooo happy!