You may have answered your own question.   It's that time of year when pollen levels are rising and are wreaking havoc on people with allergies. Being outdoors for prolonged periods of time can increase your exposure to pollen and other allergens (such as mold spores or animal dander). Also, if you're jogging or running, think how much deeper and faster you breathe -- that's more air and more allergens coming into your nose.   See your doctor. It may help to take allergy medicine BEFORE you go jogging or change the time of day you jog to a time with a lower pollen count. Or you may need to take your exercise routine indoors.