Rebound congestion?

I breathed freely last night, but now I have congestion. Can the nasal pillows cause congestion? Or is this some sort of rebound effect occurring once the air was stopped?

Have you got seasonal allergies that act up at this time of year? If so, the CPAP's fine filter will help with night time congestion by filtering out the allergens. But soon as you take that mask off your nose, you are breathing unfiltered air and hence the allergy symptoms return.

Nasal congestion can also be from the humidity settings. Too little or too much humidity.