To dream that you are vomiting is a subconscious clue that there is something in your waking life that you need to rid yourself of. Something or someone is causing you feelings of revulsion.
To see others vomiting is indicative of the machinations of false friends and those who would use you for what you can give or do for them.
To dream of having a hangover indicates self-delusion in your waking life. Too much may be happening at once leaving you feeling overwhelmed. It suggests that you may be overdoing something, possibly working too hard to avoid facing the realities in your home or emotional life. A hangover in a dream suggests that some time away from your current work commitments may be beneficial at this time.
Throwing up bile in a dream is a symbol of guilt or secrecy that is figuratively eating away at you. You are expelling something that is unhealthy for you thus this dream may be hinting you to openly acknowledge your guilt or reveal your personal secret so that you'll feel good again.