Baby Kittens – growth on neck and foot?

I 'VE the recently contained two kittens of the child, very very small eyes? open, is feeding on milk and soft sull'ali the kitten, they 're the mother? gone somewhere outside and one of them had on his neck and one of its points, this kind of white development, the format of what perhaps shaped like a small little capsule, and it seems to be attached to the fur or skin and all 'it won' t come off. Anyone know what this? They were living under our balcony and outdoor cats.