Food Allergy

Food allergies are an immune reaction to proteins present in certain foods, and only eight specific foods account for ninety percent of food allergies. These include milk, eggs, peanut, tree nuts, shellfish, fish, wheat, and soy. More than fifty million Americans suffer from food allergies, which can have several different clinical presentations:

• Anaphylaxis – a potentially life-threatening reaction consisting of low blood pressure, hives, itching, wheezing, vomiting, and throat swelling, potentially limiting normal breathing. Peanut allergy is the most common food known to cause anaphylaxis. 
• Food Protein-Induced Enterocolitis (FPIES) – a delayed food reaction usually occurring two to four hours after ingestion of an allergen, most commonly milk or soy found in baby formula. It can result in vomiting, diarrhea, and dehydration. The only way to diagnose this condition is a thorough history and administration of a food challenge in a hospital setting since skin testing is usually negative. This kind of food allergy typically resolves by age three.  
• Eosinophilic Esophagitis – an inflammatory disorder of the esophageal mucosa caused by a food allergy. It presents with difficulty swallowing, vomiting, and abdominal pain, and is typically diagnosed by endoscopy and allergy skin testing.  
• Atopic Eczema – food allergies are a well-known trigger for atopic eczema, usually in children under the age of four. While often helpful with diagnosis, allergy skin tests need to be interpreted with caution in this age group as false positives are common and confirmation of the food allergies should be confirmed with a food challenge.
• Allergic urticaria (Hives) – Food allergens are a potential cause of hives, and skin allergy testing can be an important part of the workup for a patient experiencing urticaria.  
• Oral Allergy Syndrome – a reaction caused by raw fruits or vegetables and presenting as itching and swelling of the mouth, lips, tongue, and throat. Cross-reactivity with pollen allergens is typical of this disorder. Birch tree pollen-allergic patients can react to apples, kiwi, carrots, and celery, while ragweed-allergic patients can react to bananas, cantaloupe, and watermelon. Anaphylaxis has been reported, but most reactions are transient and do not require treatment. Allergen immunotherapy for the patient’s pollen allergies may improve sensitivity to the causative fruit.