Coughing up mucous, or seeing mucous come out of your body, is a negative dream symbol.
This dream may mean that you need to put some distance between yourself and someone who’s not good for you.
It may also indicates that you have made a negative choice in some important matter.
Alternately, it can represent the dreamer’s general fear about the future.
If you dreamed of seeing mucous that did not come from yourself, you are having trouble trusting someone.
This could be wise – someone may be trying to take advantage of you in some way.