it sounds like a form of Asthma, as it is triggered by cold and fragrances. Have you seen a Pulmonologist? They specialize in asthma, lungs, and allergies.
An antihistimine can help, and sometimes a cup of coffee. Pressing your tongue hard to the roof of your mouth for several seconds will sometimes stop a cough.
I have asthma and am taking Grapeseed extract - I hardly ever use my inhaler anymore and stopped using corticosteroids (I became allergic to them).
Hope this information is helpful - wishing you the best
I have the same symptoms and have had all the tests that you have had done. The only tests I haven't had done are Allergy tests .
I am in the process of making enquiries about getting some done.
Please let me know if you get any answers and I will do the same