Tips for reducing asthma attacks

Hello all

I am hoping to get some advice.

My niece has recently been diagnosed with asthma, she is two years old.

When she is at home she has a lot of coughing fits, yesterday was quite bad and resulted in her being sick (when she has a coughing fit she has a blue inhaler to take). Over the weekend she came to stay with me and was fine - almost no coughing or chesty symptoms at all.

Both my house and my sister's houses are similar, both clean, both without pets. We are wondering if perhaps it could be to do with the air as I live in the countryside, she lives in a built up area near to a busy road.

Does anyone have any tips on how to make houses less likely to trigger asthmatic symptoms such as a dehumidifier or air purifier? My sister was thinking of getting a fan just to get some air going through the room but am I right in thinking this isn't really going to help? One of the issues is that she has only got a 'big window' in my niece's bedroom and so keeps this locked at all times. Is it better to have a window open?

Any help you could provide will be gratefully received as we are both new to this!

Danielle