I have suffered from allergies for years and at night my nose would basically close up and add to my breathing problems.  I have found that by using the nose pillows at night, if I lay down and wear the nose pillows and open my mouth the vast majority of the congestion in the sinuses and tubes leading from the ears to the throat will be cleared of congestion in 3-5 minutes.  Sometimes I can hear a gurgling sound that indicates the congestion is being forced out of the sinuses and allowing me a much better night's sleep.
This may not be the intended benefit however for me it is wonderful since I live in the country and we have all sorts of allergies causing little things in the air all the time.