Food Allergies are increasing in frequency, now affecting 8% of young children and almost 5% of adults. Food Allergies, which are immunologically adverse reactions to foods, must be distinguished from Food Intolerances, which result from other factors such as lactose deficiency.
While numerous foods can cause allergic reactions, a few classes of foods are responsible for the vast majority of food allergies. In young children, milk, eggs, and peanuts are responsible for most of the food allergies, while peanut, tree nuts, fish, and shellfish account for most of the food allergy in adults. In adults and older children, most of the food allergies are lifelong, whereas in children less than 5 years old, most will develop a tolerance to milk and eggs. Some even develop tolerances to peanuts. Oral Allergy Syndrome is an interesting subclass of Food Allergies in which patients develop mild oral and perioral pruritis, tingling, and angioedema to certain raw fruits and vegetables because the fruits and vegetables share allergenic proteins with unrelated plant pollens. For instance, patients with birch pollen allergy may develop oral symptoms to raw carrots, apples, pears, and kiwi.
Allergic reactions to foods vary from mild discomfort to life-threatening anaphylaxis. Oral Allergy Syndrome reactions are uncomfortable, but rarely life-threatening. Some eczema patients will experience flares when they eat raw fruits and vegetables associated with their pollen allergies. Acute Urticaria is a common manifestation of food allergy (Food Allergy is not usually associated with Chronic Urticaria), and may be associated with respiratory compromise from oropharyngeal swelling. Patients with a history a mild allergic reactions to foods are at risk for severe reactions on re-exposure, including nausea, vomiting, diarrhea, wheezing, and cardiovascular collapse; It is essential that all patients with a history of systemic allergic reactions to foods be counseled to avoid the foods completely and to carry and know how use an Epipen.
Patients with peanut or tree nut allergy, even those with a history of mild reactions, are the most common victims of fatal anaphylaxis to foods. Most patients with fatal or near-fatal anaphylaxis also have a history of asthma. Having and knowing how to use an Epipen dramatically decreases the risk of a fatal anaphylactic reaction, although is not foolproof; 10% of victims of fatal anaphylaxis do receive Epinephrine in a timely manner.
As with most diseases, the medical history is the single most important tool in the diagnosis of food allergy. Skin prick testing remains the single most accurate method of diagnosing a food allergy, while in vitro assays such as IgE RAST and ImmunoCAP play an important role as well. Occasionally, physician monitored oral challenge is required to confirm the diagnosis of a food allergy or to determine whether a patient has become tolerant to the relevant food.
Oral Allergy Syndrome may respond to immunotherapy to the relevant pollens, but for all other food allergies Avoidance in the mainstay treatment. This is a drastic therapy for many patients, and it is unfortunate that many are placed on overly restrictive diets based on erroneous diagnoses. It is important to select the appropriate tests and to apply them to the clinical history to ensure that the diagnosis is accurate. Patients at risk for anaphylaxis should always have an Epipen with them. Young children should be retested at intervals to determine whether they have developed tolerance.
About The Author
Dr. Gary B. Moss received a BA in Biology from the University of Chicago and an MS in Human Physiology from Georgetown University. He graduated from the Medical College of Virginia, where he also completed his Internship and Residency in Internal Medicine. He served as a Fellow of Allergy and Immunology at Barnes-Jewish Hospital and Washington University at the St. Louis School of Medicine.
He is Board Certified in Internal Medicine and in Allergy and Immunology. Dr. Moss is on staff at Sentara Norfolk General Hospital, Sentara Leigh Memorial Hospital, Bon Secours De Paul Hospital, and Chesapeake General Hospital.