It took me long time before I realized that earbud headphones (earphones) are the cause of my chronic cough. It might have been a synergic effect of allergic rhinitis, asthma and earphones, but the earphones were clearly the major causative factor, which can be explained by ear-cough reflex. As the earbud do not go too deep into ear cannal, provocation was mild and the relationship hard to discover.
Given the numbers of asthmatics and MP3 players, earbuds might worsen health condition of many people. I failed to find description of similar cases, even for earplugs. Earbuds are not listed in causes of cough. How common may this problem be?