Exercise-induced allergic reactions

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Exercise-induced allergic reactions occur during or after exercise.

Exercise can trigger or worsen asthma or, rarely, a severe allergic (anaphylactic) reaction.
Doctors usually base the diagnosis on symptoms and their relationship to exercise.
Drugs used to treat asthma can usually prevent symptoms from developing during exercise, but becoming more physically fit and gradually increasing the intensity and duration of exercise also helps.

(See also Overview of Allergic Reactions.)
Exercise can trigger the following:

Asthma: Exercise often triggers an asthma attack in people who have asthma, but some people have asthma only when they exercise. Exercise may trigger or worsen asthma because breathing fast cools and dries the airways, and as the airways warm again, they narrow. Exercise-induced asthma is more likely to occur when the air is cold and dry. The chest feels tight. People may wheeze, cough, and have difficulty breathing.
Anaphylactic reactions: Rarely, vigorous exercise triggers a widespread, potentially severe allergic (anaphylactic) reaction. In some people, this reaction occurs only if they eat a specific food (especially wheat and shrimp) before exercising. Breathing becomes difficult or blood pressure falls, leading to dizziness and collapse. An anaphylactic reaction can be life threatening.

Typically, symptoms triggered by exercise—asthma or an anaphylactic reaction—occur after 5 to 10 minutes of vigorous exercise. Sometimes symptoms begin after exercise has stopped.