Ear infections are not contagious to my knowledge and as long as the child is feeling well enough and not in pain, I would accept them. I am not sure if sinus infections are contagious, but again, I would say as long as they are well enough to not need tylenol or advil then they can come. I will give antibiotics, but not over the counter meds. So if there is fever etc, the child has to stay home.