Occasionally after I finish running I will be overcome with an urge to gag and a feeling like I have a ball of phlegm stuck in my throat. I usually end up on my knees hacking and spitting up phlegm and then five minutes later I am fine. During the episode my mouth is extremely dry. I have tried varying what I eat before running and that has not mattered. I usually run in the morning and have just a piece of chocolate and some espresso prior to the run. It is very hot in Austin, Texas so I usually run early in the morning.
This reaction never happens during the run and never immediately upon stopping. It is always between 1 to 3 minutes after I have finished a run. It usually happens after harder runs, but has also occurred after long slow runs. The runs vary in distance between 5K and 5 miles.
I would really like to know what is causing this, what I can do to stop this from happening, and if this is dangerous in any way.