My two older children suffers from allergies to dust mites. So, when they were young, they were often plagued with asthma attacks and bouts of endless sneezing. Lucky that they have outgrown this condition.
However, I am still very careful with their surroundings. I change their bedsheets very often, like once a week. Then, I also ensure that the air is clean as they are susceptible to sneezing if there are dusts and other particles in the air. I have an air purifier in their bedroom so that they can sleep better.
Nowadays, with so much haze and smog, it is good to have something like these Austin Air air purifiers. With the summer months, there is even more reasons to think about it.