This topic was on my brain last night, so I did a little (very little) bit of research. I couldn't
do any empirical testing because it was very nearly 50F when I ran yesterday, but it'll be very cold
before the end of the week.
When you exercise, your nasal passages open up. I'm no doctor, but exercise has a vasoconstricting
effect on the tissues in your sinuses. I REALLY know about this because a face plant into a car
during a bike vs. car accident caused me to have a permanent closure in the right side of my nose -
no air ever gets through - except when exercising - the passages open up a bit.
Additionally, exposure to cold air causes more mucus to be produced to counteract the drying effect
of moving all of that additional air over the surfaces of your nasal cavity and throat/mouth, and to
protect the nasal passages from cold damage.
Most every runner has noticed the effect. Sometimes when running in the cold your nose will run
like a faucet. Indeed, its just a reaction to cold air, you don't need to be exercising to notice
it - just sit outside and watch a football game in the cold, or walk the dog. Your nose will
start to run.
Is it this "nose running" that has you thinking you have a cold? Your "faucet" may take longer to
turn off than others. Are you getting stuffy? Might be exposure to dry outside air - maybe you have
a hypersensitivity to cold, dry air.
But you can't get a cold simply from running outside. Ever had a cold that lasted only one day? Real
colds don't last a day.
Might be that you just need regular exposure and your body will adjust. Might be a nasal spray.
After experimenting with just a saline spray - give Afrin a shot or two, it might not solve the
problem, but reduce the symptoms.
Hope this helps some.