These allergens, when exposed to initiate immune mediated reactions which will result
in the symptoms you experience. The allergic history usually runs
in families. Asthma can be detected by a spirometry test, and it may not be detected with an x ray or a CT scan.
So, the problem can be tackled at three levels.
At the allergen level, where you can consult an allergy specialist, who after doing some skin tests, will be able to specify some allergens.