An allergy known as exercise-induced anaphylaxis can cause facial swelling during exercise. If you suffer from this symptom, seek immediate medical treatment -- the symptoms can proceed quickly to swelling of your airway that makes it difficult for you to breathe. Fortunately, exercise-induced anaphylaxis almost certainly won't kill you, but it can cause a nasty reaction.
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An exercise-induced allergy occurs mainly in people who have food allergies, according to the University of Maryland Medical Center. An exercise-induced allergy can result in a serious allergic reaction, including facial swelling, hives and leg itching, difficulty breathing, heart palpitations and feelings of dizziness or lightheadedness. You may also faint or throw up.
You may trigger an exercise-induced allergic reaction by eating an allergy-inducing food a couple of hours prior to exercising, according to the December 2008 edition of "The Physician and Sports Medicine" journal. Common triggers include tree nuts, shellfish and fish.
If you have food allergies, avoid those foods scrupulously prior to exercising. You may also potentially head off a serious reaction if you notice symptoms such as facial swelling during exercise and immediately stop your physical activity.
If you have a full-blown allergic reaction to exercise that includes facial swelling, hives, feelings of faintness and difficulty breathing, seek emergency medical assistance. Since you can't tell how far your reaction will progress, try to stop it in its tracks. A physician can administer a shot of a drug called epinephrine to halt the reaction.