Phlegm when running, what do you do?

I really had high hopes that my allergies were just that.  That lead to a cold that turned into a secondary infection and a 10 day regimen of antibiotics. Well, finally this week I am finally well, except phlegm that sits at the back of my throat leading to gagging and coughing. My wife calls it my old man cough.   But really it is caused by foamy bubbles that sit right at the top of my esophagus.

Obviously I am not running.  But it does remind me of my last half marathon.  In the last couple of years I have found that there are times when I have this problem when running.  It especially happens when I eat gels or any "juicy" candy.   

When the gag reflex occurs when I run, I start hacking so badly that I feel like I am going to blackout.  So I have a little bit of phobia when it happens.  Because of this, gels just don't work and I have to find other nutrition.  That's not a problem on trail runs.  I love the salted potatoes or chips and watermelon.  However, on road races I am a little up a creek and find I have to slow down and either eat a nut butter or gel, wait until it has cleared and then start up again.

When you Google this subject you will find that causes can be asthma, hydration,  or allergies.  One thing I can tell you is that when I am lighter (under 210 lbs) I don't have this problem and no one could suggest that I am under-hydrated .So it is probably weight related (I am at 240 right now).

How do you control your phlegm when running?