The following quote is from pollen.com
"For patients who cannot or prefer not to use drug therapy, humidified warm air is an alternative treatment. By inhaling humid air 42 to 44 degrees Celsius through the nose for 30 minutes, two to three times a week, nasal obstruction can be reduced. Patients should discuss any treatment options with their doctors."
FYI, Andy
humidifed air helps allergy symptoms
Heated humidification helps allergy sufferer
I had allergy problems nearly my whole life. As soon as I started cpap therapy (12/27/2005) my allergy problems greatly improved (knock on wood). The filtered air may have helped some, but I am sure the heated humidification made the big difference.