Frequently after running hard workouts outside, i will break out in hives and eyes swell almost completely shut immediately upon finishing. why?

Urticaria?: This sounds like an exercise-induced urticaria. This can be histamine-induced. Consider taking an antihistamine such as claritin, (loratadine) Allegra or zyrtec 2-4 hours prior to your hard workouts. If this does not help, then it's time to see a primary care physician, an allergist or a primary care sports medicine physician.

? Allergic reaction: Your description could be related to an allergic reaction either to something outside, on your workout clothes, or one of your facial and/or hair products. I would consider taking anti-allergy meds and seeing your regular doctor.

Physical urticaria: These are hives and swelling caused by something in the environment but not necessarily allergies. In particular is one called cholinergic urticaria that is frequently brought on by exercise or heat. This is treatable, usually, with antihistamines but they need to be used before the hives. But there are other causes so you should be diagnosed and treated by a doctor you can visit.