Why do our faces get bloated while we sleep?

Could be several reasons: 1, eating lots of carbs - especially before bedtime - because they cause water retention in the tissues. 2, dehydration - the body compensates for water loss by storing more water in the tissues (and people tend to get more dehydrated at night by not drinking as much water as we do during the day). 3, alcohol consumption (done more frequently at night, also causing dehydration).