Yeah, I'm sure they do. I've got so many low-moderate level allergies that it's kinda hard to establish what normal even really feels like. I got a round of shots as a teen that helps, but it's still some level of congestion at the best of times. Actually the biggest difference I found when I first started on it (almost 10 years ago now), besides the obvious sleep stuff, is that the humidifier keeps me from getting nosebleeds about 3 times a week in the winter.