Yellow or green snot is not permitted at my dayhome so if his snot is yellow or green I would take a picture of it to show the parent and say he needs to be looked at by a dr and I need a note to say its not contagious and that its ok to come to daycare..... But since he's already given it to his sister I'm sure you won't get a note ; ) maybe a long weekend at home will be just what they need.