My one year old vomited milk then followed by yellow bile today. she has been having allergen for the past three days. is there a way to help her?

Bile is always a : Concern. If it truly was bile, you need to take your child to er. On the other hand , it may just be choice of word . Sounds like your child is irritated by the thick mucus behind the throat , which got worst with the milk. Thick mucus caused your child to gag and eventually vomited the " yellow bile" you described. If abdomen is distended , tender and still having bile vomitus , go to er now!