Anaphylaxis is defined as a potentially life-threatening generalized or systemic hypersensitivity reaction involving several organs and systems, particularly the skin, respiratory tract, gastrointestinal tract, and cardiovascular system . It is believed that the first description of an anaphylactic reaction came from François Magendie in 1839 , while the term anaphylaxis was first used by Portier and Richet  in 1902.
There is no unified method of obtaining data about anaphylaxis; thus, its incidence is very difficult to evaluate clearly. Epidemiologic studies have reported a range of 8 to 50 per 100,000 person-years, with a lifetime prevalence of 0.05% to 2.0% . A recent study from the United Kingdom reported the prevalence of anaphylaxis to be 32 in 100,000 . General opinion suggests that the prevalence of anaphylaxis is underestimated and has increased in recent years. It is also presumed that there are about 50 to 2,000 episodes per 100,000 persons, and anaphylaxis might affect up to 2% of the Western population .
Since the early-1980s, interest has grown in patients with anaphylaxis triggered by exercise. The first case report came from Maulitz et al.  in 1979. They described a patient who experienced on two occasions anaphylactic symptoms caused by running that was preceded by shellfish ingestion 5 to 24 h earlier. Both strenuous exercise and causative food alone were well-tolerated. Kidd and coworkers  presented four such patients and designated the phenomenon of food-dependent, exercise-induced anaphylaxis (FDEIA).
In 1980, Sheffer and Austen  presented a series of 16 patients in whom exertion elicited a variety of anaphylactic symptoms, including generalized urticaria, pruritus, angioedema, gastrointestinal colic, and hypotension. As this set of symptoms was very similar to anaphylactic syndrome resulting from contact with foreign antigen, they termed it exercise-induced anaphylaxis (EIA).
Patients with EIA are approximated to represent about 5% to 15% of all anaphylactic cases . Prevalence of FDEIA is not well-documented, but it is estimated to make up one third to one half of all EIA patients. In a population of more than 76,000 Japanese junior high school students, Aihara et al.  found only 13 (0.017%) and 24 (0.031%) cases of FDEIA and EIA, respectively.
There is no known racial predilection for EIA. As for other cases of anaphylaxis, prevalence of EIA by gender changes with age. In the study by Aihara et al. , there was no gender predilection in EIA patients, while in the FDEIA group, the number of boys (n = 11) was significantly higher than that of girls (n = 2). When both children and adult EIA patients are considered, the overall incidence is highest in women. In two large studies of 199 and 279 EIA patients, respectively, the ratio of females to males was 2:1 [12, 13]. Onset of EIA symptoms most typically occurs in young adulthood, predominantly in the second  or third  decade of life, but may vary from younger than 5 years of age to older than 75 years of age.
Symptoms of EIA are usually triggered by exercise of moderate intensity. Activities most commonly considered to be causative of EIA (ie, the most often reported to be associated with EIA) are listed in Table 1. There is no entirely safe exercise for patients with EIA. Symptoms may develop just as commonly in individuals performing mild physical effort such as yard work as they do in vigorously exercising athletes. Exercise with less cardiovascular demand seems to be safer and is responsible for less than 2% of EIA episodes . Episodes of EIA are not fully predictable. In some patients, exercise of the same intensity sometimes provokes symptoms, but on other occasions, a patient will remain symptom free. It seems plausible that some external factors may influence EIA. Warm environment, high humidity, and cold environment have been reported to be associated with EIA occurrence among 64%, 32%, and 23% of patients, respectively . Frequency of EIA events varies from patient to patient and ranges from singular episodes to multiple episodes too frequent to enumerate. Shadick et al.  reported an average of 14.5 attacks per year. Most patients claim that the frequency of EIA episodes remains stable or decreases after the illness first begins. The most frequently reported symptoms are listed in Table 2.
In the subpopulation of patients with FDEIA, ingestion of causative food and physical effort are necessary to induce anaphylaxis. In Europeans, tomatoes, cereals, and peanuts are the most frequent allergenic foods , whereas in the Japanese population, wheat and particularly the omega-5 gliadin allergen are the most frequent [15, 16•]. Other causative foods include seafood (especially shellfish), seeds, cow’s milk, some vegetables and fruits (eg, oranges, onions, or grapes), foods contaminated with aeroallergens such as house dust mite and Penicillium mold, meats, and miscellaneous foods (eg, alcohol, snails, taro, red bean, and mushrooms) .
Symptoms of EIA may start at any stage of exercise or after it, but in 90% patients, they begin within 30 min after initiating exercise . In FDEIA, ingestion of causative food usually precedes exercise by several minutes or even hours. However, some observations indicate that FDEIA may also occur if the food is ingested soon after the completion of exercise. Thus, it seems very likely that in FDEIA, not the sequence but rather the coincidence of triggering factors is of crucial importance.
Clinical history of EIA does not differ significantly from that of anaphylaxis triggered by other factors. In the historic paper by Sheffer and Austen , four stages of an EIA event were distinguished: prodromal, early, fully developed, and late. The prodromal symptoms manifest with fatigue and prostration and generalized pruritus with erythema. The early stage is characterized by generalized urticaria. If the event progresses, fully developed EIA includes gastrointestinal symptoms with abdominal cramps, nausea, and vomiting, as well as symptoms of upper airway obstruction with dyspnea, stridor, and a feeling of choking. Symptoms of the late phase—frontal headache and fatigue—may be present up to 72 h after the onset of EIA. Of course, this description does not include all manifestations. In a fully developed EIA attack, the spectrum of symptoms is wider and may be much more severe. Some patients develop symptoms from the lower airways, including dyspnea, wheezing, and chest tightness. Cardiovascular symptoms, including collapse or altered consciousness, are reported in one third of EIA patients . Fatalities or near-fatalities are very rare [17–19], but EIA must be considered as a potentially life-threatening condition.