It is well known that exercise can induce systemic reactions, even anaphylactic shock, in some patients suffering from food allergy. Typically, exercise-induced anaphylaxis occurs on exercise immediately after the ingestion of a specific food. Nonetheless, it can occur also in the postprandial state without the certain identification of a specific causative food. In addition, the occurrence of anaphylaxis when the responsible food is ingested immediately after the exercise has been described (1). Food-dependent exercise-induced anaphylaxis has been variously associated with cereals, seafood, peanuts, tree nuts, eggs, milk and vegetables. We describe herein a severe anaphylactic reaction after exercise and milk ingestion in a child who previously underwent a successful desensitization protocol for cow milk (CM) allergy.
The patient was a 9-year-old boy who was diagnosed as having CM allergy at the age of 8 months. The clinical presentations of his CM allergy were urticaria, angioedema and wheezing. The diagnosis had been supported by skin prick test, CAP-RAST assay, and double blind, placebo-controlled food challenge (DBPCFC). Skin test was carried out on the anterior forearm surface with the prick by prick technique using undiluted CM. A negative control (saline solution) and a positive control (histamine 10 mg/ml) were also used (2). The patient showed an 8-mm-positive prick by prick test. The RAST assay (CAP system; Pharmacia, Uppsala, Sweden) gave a value of 4.80 KU/l for CM-specific IgE (normal value <0.35 KaU/l). The DBPCFC with CM and soy formula as placebo, performed at the clinic with full facilities for resuscitation, confirmed the diagnosis of allergy to CM. After the diagnosis was established, the patient began strict allergen avoidance and underwent a new food challenge every subsequent year, in order to verify if a remission had occurred. In fact, CM allergy usually remits or attenuates after 3 years of age. In our case, because of the persistence of symptoms confirmed by a stably positive food challenge, we decided to attempt a desensitization (tolerance induction), with slowly increasing doses of CM. The desensitization lasted 180 days, starting with two drops of cow's milk diluted 1:25 and progressively increasing, until a dose of 200 ml of milk (3) could be tolerated.
The protocol of oral desensitization was completed with limited side effects including: localized urticaria, stomach-ache and oral itching. These side effects were mild and self-resolving and required no treatment; but one episode of urticaria was easily controlled with oral antihistamines. At the end of the desensitization, the oral food challenge was negative and the boy could drink regularly about 300 ml of milk daily for breakfast. On one occasion, the boy participated in a football match just 30 min after having breakfast with the usual dose of milk. At the beginning of the second run, he suddenly developed generalized urticaria, angioedema, wheezing and dyspnoea. He was immediately treated on the field by the sports physician with intramuscular adrenaline, dyphenhidramine and betametasone. He was then admitted at the EC unit, where he gradually recovered. Two months later, he was admitted to the emergency department with a similar major episode, which occurred again during strenuous exercise following ingestion of cow's milk.
After these episodes, we ascertained that the patient could freely drink milk, without subsequent physical exercise, and that physical exercise (full football match) without previous ingestion of milk did not provoke symptoms. The parents were then informed about the possible association of milk ingestion and exercise and were advised to get the boy to avoid milk at least 3 h before any exercise (4).
The body of evidence concerning ‘specific oral induction tolerance’ for food allergy in humans is rather poor and it is not known how much effective and persistent this tolerance is (5). We report herein, for the first time, a case of successful induction of tolerance to a food with the subsequent appearance of severe exercise-induced symptoms. Thus, we notice, and advice, that achievement of induced tolerance to milk may be only partial and that the tolerance can be overcome by a relevant nonspecific stimulus such as strenuous exercise. In addition, the possibility of a ‘recall food allergy’ should be suspected after exercise (6), which follows the ingestion of food(s) previously tolerated.