What Is Exercise-Induced Anaphylaxis?

Exercise-induced anaphylaxis is a rare, and serious, allergic reaction. It is a severe allergic reaction that is caused by exercise. It is typically caused by medium- or high- exertion activities like running. It is typically not caused by less strenuous activities like walking.¹

What causes exercise-induced anaphylaxis?

We do not know exactly what causes exercise-induced anaphylaxis. Anaphylaxis is the name for a serious allergic reaction. In anaphylaxis, your immune system overreacts to something and releases chemicals. These chemicals, like tryptase and histamine, cause the symptoms of the allergic reaction.¹

For some people, eating certain foods minutes to hours before exercise can cause a reaction. This is called food-dependent exercise-induced anaphylaxis, or FDEIA. If they eat these foods without exercising, their bodies will not react. But exercising within a few hours after eating these foods can cause anaphylaxis. Foods that may trigger it include:^1,2

• Wheat and grains (most common in Western populations)
• Shellfish (most common in Asian populations)
• Certain meats like beef and pork
• Eggs
• Fish
• Milk
• Nuts
• Soy
• Certain fruits and vegetables like apples or peaches

Exercise increases your heart rate. One idea scientists have is that this increased heart rate causes faster blood flow. The faster blood flow could mean your body absorbs more of a certain allergen from your bloodstream. However, this idea is not proven.¹

For some people, other factors can make exercise-induced anaphylaxis more likely. This means while exercise is the main trigger, these factors can make a reaction more likely. These factors include:³

• Alcohol
• Certain painkillers called nonsteroidal anti-inflammatory drugs (NSAIDs)
• Being in certain phases of the menstrual cycle
• Extreme cold or hot temperatures
• Exposure to high levels of pollen
• Illness

How rare is exercise-induced anaphylaxis?

More research is needed to understand how rare exercise-induced anaphylaxis is. One study from Japan found that about 3 of every 10,000 people had exercise-induced anaphylaxis. The same study found that about 17 of every 100,000 people have FDEIA. However, one study's findings are not enough to be certain about exactly how rare it is.^2,3

What are the symptoms of exercise-induced anaphylaxis?

The symptoms of exercise-induced anaphylaxis may happen at any time during exercise. Anaphylaxis is a life-threatening reaction. Symptoms may include:^1,2

• Coughing
• Difficulty breathing or feeling like your throat is closing
• Feeling dizzy
• Feeling flushed and warm
• Itchiness
• Swelling
• Hives
• Upset stomach
• Vomiting or diarrhea
• Loss of consciousness

How is exercise-induced anaphylaxis diagnosed?

There is no single test for exercise-induced anaphylaxis. This can make it difficult to diagnose. Often, your doctor will have to ask about the events that led up to anaphylaxis. With a detailed history, they may be able to make a diagnosis. They may use a blood test to look for signs of an allergic reaction.^1,3

Your doctor may use a scratch test to identify triggers for FDEIA. In a scratch test, a thin needle is used to expose you to very small amounts of potential allergens. This can identify things you are allergic to in a safe way.^1,3

Your doctor may suggest an exercise challenge test. In this test, you will follow your doctor's instructions to trigger anaphylaxis by exercising in a safe environment.^1,3

If you have FDEIA, a challenge test may involve eating a small amount of the food you may be allergic to and exercising. For example, you may run on a treadmill. If you go into anaphylaxis, your doctor will be able to treat it. Not all doctors agree that this type of testing is safe. So, it may not be a good fit for you.^1,3

For FDEIA, your doctor can use food avoidance as a diagnostic tool. You may be instructed to stop eating for 4 hours before exercise to see whether your symptoms are linked to food.⁴

How is exercise-induced anaphylaxis treated?

Having exercise-induced anaphylaxis does not mean you cannot exercise. There are many health benefits to exercising. It does mean you may have to pay attention to your triggers. It helps to identify how hard you were pushing yourself when you first experienced the symptoms. In the future, try to stay below this threshold.^1,3

Other things to keep in mind include:^1,2

• Stop exercise at the first sign of anaphylaxis symptoms.
• Carry an epinephrine auto-injector, like an EpiPen®, when you exercise.
• Work out with someone who knows about your exercise-induced anaphylaxis and knows how to use your EpiPen.
• Avoid exercising in extreme temperatures.
• Avoid potential co-triggers such as NSAID painkillers and alcohol.

If you have to use your EpiPen, always call 911 after. You may need additional care, and this helps you get immediate help.¹

For food-dependent exercise-induced anaphylaxis, avoiding the triggering food 4 hours before exercise should prevent a reaction. Your doctor may increase or decrease this avoidance time based on your symptoms.⁴