DD (5) has always been a very snuffly child even when not ill with a cold, suspected hay fever although usually only in the summer. The past 3 nights she's had a really blocked nose at night, brings up all the mucus in the morning when she wakes up (sorry TMI!), then nothing all day. Only at night! Every night when I'm sat up with her because she can't breathe I'm expecting a full blown cold to develop, then it doesn't. What could it be? We have an air purifier on in the room every night and she has Piriton before bed.