As long as it stays in the diaper I tough it out especially with the youngest because other factors such as teething or a change in diet can be the cause over illness. Once it escapes the diaper I go by the number of changes of clothes the child has. Once the last outfit is on they have to go home cause there is nothing left for me to use. An older child is different in that it is generally totally out of character for the child and I am less likely to have enough changes of clothes for them. Because I can not control everything that child touches or does for the day I prefer they go home till we rule out illness - saves on my cleaning.