This is a fungal infection of the mouth, caused by yeast: Candida albicans. Yes the same culprit that cause yeast infection in adults! Normally Yeast exists freely on the body and in the mouth, but sometimes it grows out of control, especially when the immune system is overwhelmed. When that happens in the mouth, white patches develop on the tongue and the inside of the cheeks.

Nappy rash is sometimes caused by thrush, a fungal infection. ... It's also possible for your baby to have fungal nappy rash even if she isn't taking antibiotics. In some cases, babies with oral thrush pass the fungus through their digestive system and into their poo, infecting the nappy area