Food Allergy: What You Need to Know

Stephanie A. Leonard, MD


November 15, 2010

In This Article

Conditions Associated With Food Allergy

Oral Allergy Syndrome

Oral allergy syndrome (OAS) is caused by proteins in fresh fruits, vegetables, and nuts that are homologous with proteins in pollen.[66] Up to 50%-75% of individuals who suffer from pollen allergies are estimated to be affected.[67,68] Classic examples of pollen-food associations include birch with apple, peach with hazelnut, and ragweed with banana and melon.[69]

Symptoms are typically limited to oral pruritus and mild angioedema, with occasional rhinitis and facial rash. Because these homologous proteins are heat and acid labile, they are broken down easily by stomach acid and destroyed in cooking; therefore, symptoms are rarely systemic.[70,71] Many patients continue to eat these foods in their fresh states despite the oral discomfort, and most patients report being able to tolerate the same foods when cooked or processed. One study showed that symptoms of OAS can become systemic in 8.7% of cases, and 1.7% experience anaphylaxis.[72]

Treatment of OAS involves avoidance and treatment of symptoms with antihistamines and/or epinephrine if the reaction is systemic or severe.

Food-Dependent Exercise-Induced Anaphylaxis

Food-dependent exercise-induced anaphylaxis (FDEIA) is a rare condition in which symptoms develop if food (or a specific food) is eaten within 2 hours prior to exercising.[73]

The most common food implicated in FDEIA is wheat, but celery, shellfish, tomatoes, grapes, chicken, dairy products, and mushrooms have also been reported, and theoretically any food can be associated with FDEIA.[10,74] These same foods are otherwise tolerated in the diet when exercise is not involved.

Factors that can be associated with triggering FDEIA include menstrual cycle, amount of food ingested, alcohol, aspirin or NSAIDs, and weather.[10] The immune mechanism for FDEIA is poorly understood, but proposed theories include altered splanchnic blood flow, stress-increased proinflammatory mediators, autonomic dysregulation, and increased intestinal permeability leading to absorption of larger peptides.[75,76,77,78,79,80]

Management of FDEIA involves avoidance of trigger foods prior to exercise, not exercising alone, wearing a medic alert bracelet, and carrying self-injectable epinephrine in case of anaphylaxis.[10]


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