It can sometimes be difficult to differentiate between a runny nose caused by allergies and one caused by exercise. However, there are a few key differences to look out for. If your runny nose is accompanied by other symptoms like sneezing, itchy eyes, and a scratchy throat, it is more likely to be caused by allergies. On the other hand, if your runny nose is primarily triggered when you exercise and you don't have any other allergic symptoms, it is more likely to be exercise-induced rhinitis.