It's a simple fact. Most allergy and asthma symptoms occur during the night when we are trying to rest.
Breathing airborne particles causes more nighttime allergy and asthma symptoms than everything else combined. The symptoms occur at night while we are sleeping because our respiratory system is also trying to rest.
Hence, the same normal air that wasn't any problem while we were awake can now bring on allergy and asthma attacks simply because our body's air cleaner has slowed down to a crawl. These are the vital eight hours when the air must be super cleaned if we want an uninterrupted sleep.
Our air cleaners have enough cleaning power to remove 85% of the airborne particles in most bedrooms in less than 15 minutes. This change in air quality is usually enough to prevent allergy and asthma symptoms from occurring while we sleep.