Exercise-induced anaphylaxis (EIA, EIAn, EIAs) is a rare condition in which anaphylaxis, a serious or life-threatening allergic response, is brought on by physical activity. Approximately 5–15% of all reported cases of anaphylaxis are thought to be exercise-induced.
The exact proportion of the population with EIA is unknown, but a 2001 study of 76,229 Japanese junior high students showed that the frequency of EIA was 0.031%.
Exercise-induced anaphylaxis is not a widely known or understood condition, with the first research on the disorder only having been conducted in the past 40 years. A case report in 1979 on EIA was the first research of its kind, where a patient was described to experience anaphylactic shock related to exercise 5–24 hours following the consumption of shellfish.
The condition is thought to be more prevalent in women, with two studies of EIA patients reporting a ratio of 2:1 for females:males with the disorder. There is, however, thought to be no link to ethnicity.
Survey results from EIA patients have shown that the average number of attacks per year is 14.5. However, most sufferers of EIA report that both severity and frequency of attacks decrease over time.
Symptoms
The anaphylaxis campaign splits symptoms of EIA into two categories: mild and severe. Mild symptoms may include "widespread flushing of the skin", hives or urticaria, swelling of the body (angioedema), swelling of the lips, and nausea or vomiting. More severe symptoms might include the swelling of the tongue, difficulty in swallowing or breathing, constriction of the airways, feeling faint, and unconsciousness.
Symptoms can start immediately following exercise, but 90% of patients report experiencing an attack 30 minutes following activity.
A paper by Sheffer and Austen (1980) splits an EIA event into four distinct stages: prodromal, early, fully developed, and late. Characteristic symptoms of the prodromal stage include redness and itching. In the early stage, generalised urticaria develops. If the reaction does not diminish, it may become fully developed EIA, in which gastrointestinal symptoms and constriction of the airway may occur. The late phase, which follows recovery from the reaction, includes frontal headaches and a feeling of fatigue; these symptoms may manifest themselves up to 72 hours following onset of the reaction.
Cardiovascular symptoms are reported in 1/3 of patients diagnosed with EIA.
Food-dependent exercise-induced anaphylaxis
Food-dependent exercise-induced anaphylaxis (FDEIA) is a subcategory of the disorder where exercise only invokes a reaction when followed by the ingestion of a food allergen. Patients whose EIA is food-dependent are thought to make up from one third to a half of all EIA cases. In a 2001 study of 76,229 Japanese junior high students, 0.017% of students were found to suffer from the condition.
In European countries, the most common trigger foods for FDEIA are tomatoes, cereals and peanuts. In Japan, FDEIA is most commonly triggered by omega-5-gliadins, an allergen found in wheat. Other common foods thought to be linked to FDEIA include shellfish, seeds, dairy (in particular cow's milk), fruits and vegetables (such as grapes, onions and oranges), meats, and even mushrooms.
Ingestion of the trigger food most often precedes exercise by minutes or hours in cases of an attack; there are, however, reported incidents of attacks occurring when ingestion transpires shortly following activity. While a lot remains unknown about the pathophysiology of food-dependent exercise-induced anaphylaxis (FDEIA), one theory points to changes in pH; this theory is based on the fact that pH becomes more acidic in the muscles and serum following exercise. Decreasing pH is associated with an increase in mast cell degranulation, a key component to the immune response, and one study found that, when patients with FDEIA are given the antacid sodium bicarbonate prior to exercise, they do not experience FDEIA symptoms.
Common triggers
Exercise-induced anaphylaxis is most commonly brought on by aerobic exercise. It is most often caused by higher levels of exertion, such as jogging, but can be brought on by milder activities, such as a gentle walk. In a 1999 study, 78% of sufferers reported that attacks were frequently caused by jogging, whereas 42% reported symptoms following brisk walking.
There are several factors outside of food and exercise that have been suggested to increase the risk of an EIA attack. These include the consumption of alcohol, exposure to pollen, extreme temperatures, the taking of non-steroidal anti-inflammatory drugs (NSAIDs), and even certain phases of the menstrual cycle.