A sneeze is the body's reaction to an irritant or allergen. Sometimes you sneeze and the irritation is gone; however, if you have an allergy, your body releases histamine. This results in multiple symptoms that may include sneezing, coughing, a runny nose or swollen eyes. Sneezing after exercise may be caused by the vigorous exercise itself or other allergens.
Rhinitis simply means inflammation of the nose. Exercise-induced rhinitis happens when your body has an allergic reaction to exercise. It may be vigorous exercise that triggers the rhinitis, or the trigger may be a combination of exercise and an allergen such as pollen or mold.
Photic Sneeze Reflex
If you exercise indoors and then step out into bright sunlight, this may trigger your photic sneeze reflex. The trigeminal nerve controls sneezing, and the photic reflex is caused by a congenital deformation of that nerve, which sends signals to the brain when overstimulated by bright light.
Walking from one temperature into another may make your nasal membranes contract and cause sneezing. If you get hot while exercising, and then you walk into a cool room, the temperature difference may trigger a sneeze.
Pollen and Grass
Walking or exercising outside may trigger sneezing if you have an allergy to pollen or grass. Breathing heavily during exercise will make your reaction worse, as you will draw more of the irritant into your respiratory system.
Mold may grow anywhere there is excessive moisture, poor ventilation or high humidity. Breathing in mold spores may cause an allergic reaction and sneezing. Allergies may be hereditary, so sensitivity to mold may run in your family. Mold may grow behind walls or in air ducts, so it is not always easy to see. Because you tend to breathe more heavily during exercise, you may breathe in more spores, making the allergy worse.