Exercise-induced anaphylaxis (EIA) is a rare yet serious allergic reaction that occurs during or after physical activity. While exercise alone can sometimes trigger an episode, for many individuals, it happens when other factors are involved.
Understanding Exercise-Induced Anaphylaxis
Exercise-induced anaphylaxis involves a complex immune response. Specialized immune cells called mast cells, found throughout the body, activate and release chemicals like histamine into the bloodstream. This release causes the wide range of anaphylactic symptoms.
This condition differs from other exercise-related issues, such as exercise-induced asthma, which primarily affects the airways. While exercise can exacerbate asthma, EIA represents a systemic allergic response affecting multiple organ systems. The reaction is not a typical allergic response to something external like pollen or a bee sting, but rather an internal response to physical exertion, often in combination with other internal or external factors. The exact mechanism causing mast cells to degranulate during exercise is not fully understood, but it involves a lowered threshold for their activation.
Recognizing the Symptoms
The symptoms of exercise-induced anaphylaxis can appear rapidly, often within 30 minutes of starting exercise, but they may also manifest later or after physical activity has ceased. Initial signs can include a feeling of warmth, generalized itching (pruritus), and flushing of the skin. These early manifestations can progress to more severe symptoms if exercise continues.
Skin reactions are frequently observed, presenting as hives (urticaria) and swelling (angioedema) affecting various parts of the body. Gastrointestinal symptoms may include nausea, vomiting, abdominal cramps, and diarrhea. Respiratory distress is a serious sign, characterized by difficulty breathing, wheezing, coughing, and a sensation of throat tightness or swelling.
Cardiovascular effects can involve dizziness, lightheadedness, a significant drop in blood pressure, and even collapse. In some cases, neurological symptoms such as headache and confusion can also occur.
Common Triggers and Risk Factors
Exercise-induced anaphylaxis can be triggered by exercise alone, but often other factors contribute to an episode. One common scenario is food-dependent exercise-induced anaphylaxis (FDEIA), where an allergic reaction only occurs if a specific food is consumed around the time of exercise. Common food triggers include wheat, shellfish, nuts, milk, eggs, and various fruits and vegetables. For individuals with FDEIA, eating the food without exercising, or exercising without eating the food, typically does not cause a reaction.
Certain medications can also act as co-factors, particularly non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin or ibuprofen. Taking these medications before physical activity can increase the risk of an EIA episode. Other potential risk factors include extreme temperatures, such as exercising in cold or hot conditions, high humidity, and hormonal changes, such as those occurring during menstruation. Recent infections, stress, and alcohol consumption have also been identified as possible co-factors.
Diagnosis and Management
Diagnosing exercise-induced anaphylaxis often begins with a detailed review of the patient’s medical history and a physical examination. Healthcare professionals inquire about symptoms, their relation to physical activity, and any foods or medications consumed. Sometimes, an exercise challenge test is performed under medical supervision in a hospital setting to confirm the diagnosis and identify the specific type and intensity of exercise that triggers a reaction. Blood tests for specific allergies may also be used, particularly if a food-dependent variant is suspected.
Immediate management of an EIA episode involves stopping exercise at the first sign of symptoms. The primary treatment for anaphylaxis is the administration of epinephrine, usually through a pre-loaded auto-injector. Patients diagnosed with EIA are typically prescribed two epinephrine auto-injectors and instructed on their proper use. Emergency medical services should be contacted immediately after epinephrine is administered.
Long-term management focuses on preventing future episodes. This includes avoiding identified triggers, such as specific foods or medications, particularly before exercise. Individuals with FDEIA may need to avoid their trigger food for several hours before and after physical activity. Modifying exercise routines, avoiding extreme temperatures, and always carrying two epinephrine auto-injectors are also important preventive measures. Wearing medical alert identification can inform others of the condition in an emergency.