Sinus drainage

What could be the reason for a "bubbly" drainage from sinuses and also saliva being "bubbly"?  Is it an infection, vitamin deficiency or some other explanation?

[National Jewish]

The "bubbly" nature of the drainage does not really mean much. If it is discolored or if has a foul odor, then infection is a common cause. The "bubbly" nature of the saliva has no specific negative association to it.