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Keywords:

  • anaphylaxis;
  • food-dependent exercise-induced anaphylaxis;
  • food hypersensitivity;
  • soy

Exercise-induced anaphylaxis (EIA) is an uncommon condition. However, it is increasingly reported, possibly in relation to an augmentation of physical exercise. In one-third of the patients, anaphylactic reactions are associated with a specific food ingested before exercise, leading to food-dependent, exercise-induced anaphylaxis (FDEIA).

We report the case of a 29-year-old man who, 20 min after a submaximal effort on a bicycle and 10 min after ingestion of a Japanese drink containing soy protein, experienced an anaphylactic reaction with sneezing, nasal obstruction, generalized pruritus, shortness of breath, and throat tightness. The symptoms rapidly resolved after intravenous administration of clemastine and prednisolone.

The patient's personal and family history revealed no atopy or food intolerance.

Skin prick tests with food allergens were positive to soy (3 mm). Prick-to-prick testing with the soy drink was positive (5 mm). The size of the wheal to histamine was 5 mm. Specific IgE antibodies (CAP FEIA, Pharmacia) to soy were undetectable.

Oral challenges under resting conditions to soy and to the suspected soy drink remained negative. A food challenge associated with exercise, consisting of a submaximal effort (196 W on a treadmill) 15 min after the soy drink, was positive. Ten minutes after ending the exercise, the patient presented eyelid edema, as well as pruritus and erythema of the hands and scalp, but there was no dyspnea or modification of spirometry. The patient was instructed strictly to avoid soy. After 8 months of follow-up, he did not re-present similar reactions despite regular exercise.

Soy-related adverse reactions are mainly reported in children (1), but they may also represent an underestimated cause of severe life-threatening reactions in adults. While four fatal anaphylactic reactions have recently been reported over 3 years in young children with severe peanut allergy and asthma (2), none have been reported in adults.

A number of cofactors may be implicated in EIA, such as atopy (71%), extreme climatic conditions, and ingestion of aspirin or other nonsteroidal anti-inflammatory drugs and relevant foods (37%) (3).

The diagnosis of FDEIA is based on screening for potential food allergens by skin prick tests, prick-to-prick tests, specific IgE antibody measurement, and, in equivocal cases, double-blind, placebo-controlled food challenges associated with exercise (4). Soy allergy is rarely reported in adults. Foods are often suspected as triggers in EIA, and soy might be an unrecognized food more frequently involved in EIA than previously suspected. Complete soy avoidance, or at least avoidance of soy for 4 h before physical exercise, is an effective method of prevention in patients diagnosed with soy-induced FDEIA (4).

To our knowledge, we have reported the first case of soy-dependent, effort-induced anaphylaxis. Physical exercise and consumption of processed foods containing soy proteins are trendy. Soy allergy in adults, and more specifically in association with exercise, may increase in the future.

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