I've had this reaction for as long as I can remember; seconds after eating a conventional banana I get a slight cough, which persists for a while and then goes away. It's like I'm reacting to some gas or chemical.
This is for regular store-bought bananas. When I eat a truly organic banana I don't get that reaction. Problem is it's hard to find truly organic bananas. Even the ones labeled organic aren't always organic. A truly organic banana has a raw almost plantain look.
The culprit here is the ethylene gas they use to help ripen bananas(and other fruits). Most imported bananas are picked green or unripe and then sprayed with ethylene gas to ensure a timed ripening process. This gas, however, is toxic and your body warns you about this through the coughing process.
Bananas were once a hard vegetable with dark seeds but have been cultivated over the centuries into an edible fruit. They are reproduced through the stem and would dissapear if not for manual intervention. They have lower water content than most fruits and often leech water from the body.
I'm not saying bananas are bad. I love them and eat them everyday, but like all hybrid fruits, they come with certain drawbacks. The best bananas are grown locally, are non-GMO, and unsprayed. Limiting your daily intake to one or two bananas is best.