Had problems breathing, eyes itched, migraines nonstop. Finally went to an ears, nose, throat specialist and was diagnosed with numerous severe allergies. Started on medication but it was not doing the full job. We saw these filters and decided to try them. What a difference! I could not believe how dirty the filter was. The first time we replaced it after the three months which is recommended. We changed it monthly for three months following that than every two months for the next 3 changes. Each month it became a bit less dirty. We could not be happier with the cleaner air!