Marta, before expert opinions start rolling in, it may help to first turn your attention toward the humidity levels and ventilation in your home. Dry air can worsen asthma just as much as humid, so I think it's well worth investing in a hygrometer. Aim for 55-70% humidity and good ventilation for optimal health for your family and plants.

I find that keeping plant leaves and areas of the home dust-free helps a lot. I also open all the windows and allow fresh air in at least twice a day. Fresh, oxygen-rich air is nothing short of miraculous for the body.

If you have air circulating through A/C vents, take a look at those filters and think of how clean the A/C ducts are - that's where mold spores are thriving.

Little things, big impact is what I noticed to be true. And though I don't have asthma or allergies, I immediately start coughing when I'm in a room with dry and stagnant air.

Of course, if you suspect that a plant may in any way exacerbate your son's asthma, it's best to remove it, at least for a while.

Best wishes to your son, I hope he feels better soon.

Did you get these plants in the last year?

Typically, associations of plants with asthma are based on the pollen they produce. If none of the houseplants flower - the source of pollen - then their contribution to the irritation that triggers your son's asthma is minimal. So snip off any emerging flower inflorescence as soon as you see them and there will be no pollen issues

And only ferns have spores....'regular' plants do not. So avoid ferns. And the issue with the ficus is with the sap, which is a sticky latex that can cause skin reactions but should have no effect on an asthma sufferer. Just do any pruning outside if necessary or have your son avoid until any sap has dried and disappeared

Just keep the plants healthy, well-dusted and do not overwater. Overwatered or stressed plants can develop fungal problems and those can be a source of molds or spores, not the plants themselves. Keep an eye out for any pests and treat appropriately. In fact, you will probably find more recommendations for including houseplants in your indoor environment to improve the quality of air and reduce the asthma irritants than cautions to avoid.

unless he's specifically allergic to them id say no. I have severe asthma and for me I need to keep indoor humidity at least at 50% in the winter. Also need to keep dust at bay.

Is this something you can patch test?