Stephen
Unless you are in the room why would you run it , yes while you are sleeping is fine or awake . Been there and done it!!!!

Jeff
There is no danger in operating these types of devices. You can leave it on 24/7, if you wanted to. I would keep it on while you're at home, at the least. As for seeing results, you kind of just have to gauge how well your breathing over a period of time. There's not going to be a drastic change in air quality, but they do help reduce the amount of particles in the air, even the smaller plug in the wall types. Do you have central heat/air? Most central systems that are easily accessible and in decent shape can have a electronic air cleaner added into the airflow. You can even get a UV light system that can disinfect the air, not just trap particles in a cleaner. These types of devices aren't exactly cheap to have installed, but depending on the severity of your allergies, it might be worth it.

Musha
may u have.

docksrocks
You likely can keep it running continuously. An even better solution to your problem is to have a UV filtration system. These UV (ultra violet air filters) are mounted in the duct system of a central heating and cooling system. The UV filter does not capture/stop dust, but it kills/sterilizes the harmful dust and bacteria molecules in the air. I am not sure if you can get one for in an individual room with its own fan system like your EAC, but that would be a better system for you likely. The UV filter installed on a central Heating and AC systems duct is the best though. Then, to have a good heavy duty media filter in the system to capture the dust and pollen, would be the untimate system for you (so both types of filtration systems). The problem with any electronic air cleaner (EAC) is that it only stops a portion of the dust with every room air change cycle. The good media filters stop almost all of the dust with one passage of air.