The physicians and staff at DFAC are dedicated to the diagnosis and management of food allergies. We understand how the diagnosis of food allergy can be a life changing event with far reaching quality of life implications. The following is a summary of our current understanding of food allergies, including diagnostic methods, management strategies, educational resources and future directions in treatment. We hope that this information will address most frequently asked questions and stimulate additional discussions with our physicians and clinical staff.
FOOD ALLERGY PREVALENCE IS ON THE RISE
The prevalence of food allergies in the general population (both children and adults) has clearly increased during the last 20 years. While newly recognized food allergy syndromes, changing definitions and increased availability of commercial allergy testing methods have no doubt contributed to some degree to the rising number of food allergy diagnoses, the incidence of confirmed cases of anaphylactic (life threatening) reactions to common foods has more than doubled during this period, from approximately 1% to 2-3% of the population. Several theories have been proposed to explain the rise in food allergy prevalence, ranging from environmental influences of modern Western society to the ways in which we introduce new foods to infants and young children. However, at this time none of these theories has yielded definitive answers or practical solutions to prevent the development of food allergies.
OVERVIEW OF FOOD ALLERGY DISORDERS
PROBLEMS THAT WE EVALUATE AND TREAT
Although food allergies can present with a variety of different symptoms, the single defining feature of all food allergic disorders is an immunologic mechanism. Immediate allergic reactions (IgE-mediated hypersensitivity reactions), ranging in severity from hives to anaphylactic reactions, are among the most common problems for which patients are referred to our practice. Additional food allergy-related disorders with less clearly defined immunologic mechanisms that we evaluate and treat include atopic dermatitis (eczema), Food Protein-Induced Enterocolitis Syndrome (FPIES), and Eosinophilic Esophagitis (EoE).
PROBLEMS THAT WE DO NOT EVALUATE OR TREAT
A notable immunologically mediated food hypersensitivity disorder that we are often asked to evaluate is celiac disease or gluten sensitive enteropathy. We generally refer patients with suspected celiac disease to GI specialists for proper diagnosis and management. In addition, we do not subscribe to the rising common misconception that gluten or casein sensitivities are underlying causes of Autistic Spectrum Disorder. Additional food sensitivity complaints for which we do not recommend our services include: (1) ADD/ADHD; (2) multiple chemical sensitivities; (3) Chronic Fatigue Syndrome; (4) provocation/neutralization therapy.
IgE-MEDIATED FOOD ALLERGIES
The hallmark of these disorders is the potential for life threatening allergic reactions (also known as anaphylaxis) occurring within minutes after ingesting a tiny quantity of the suspect food. Symptoms of anaphylaxis may include any of the following: hives (welts), eye or facial swelling, throat swelling, change in the sound of the voice, cough, wheezing, difficulty breathing, abdominal cramping, nausea, vomiting, dizziness, faintness, sudden quietness, cardiovascular collapse and death. Milk, egg, wheat, soy, peanut, tree nuts, fish and shellfish account for more than 90% of IgE-mediated food allergic reactions. Milk, egg and wheat allergy often begin during the first year of life as these foods are being introduced into the baby’s diet. Allergic sensitivity to these foods often resolves after 5-10 years of avoidance. By contrast, nut, fish and shellfish allergies are usually lifelong problems.
DIAGNOSIS OF IgE-MEDIATED FOOD ALLERGIES
The proper diagnosis of an IgE-mediated food allergy begins with a carefully obtained medical history to determine which food(s) may be responsible for an observed allergic reaction. Because such reactions typically begin within 60 minutes following ingestion, we can usually identify candidate foods for testing by obtaining a detailed history of the events leading up to the reaction. Allergy testing should be limited to the suspected food(s). Appropriate methods for confirming a suspected IgE-mediated food allergy include skin prick testing and serum specific IgE antibody (blood) testing. Each method has advantages and disadvantages highlighted in the table below. Your DFAC allergist will recommend the most appropriate testing method depending on a variety of factors applicable to your specific case. Regardless of the method selected, broad spectrum or “screening” food allergy testing should be avoided because a positive test without a correlating history of an allergic reaction is often a false positive result, leading to unnecessary anxiety and dietary restrictions. Most of the time there is good agreement between skin prick testing and blood testing but, in some patients there are significantly different results. Your DFAC allergist may recommend both forms of testing in some circumstances.
|Testing Method Comparisons||Skin Prick Testing||Serum IgE Antibody Testing|
|Sensitivity in Confirming a Diagnosis of Food Allergy (With Prior Reaction History)||Excellent (>95%)||Very good (85-90%)|
|False Positive Rate as a Screening Test (Without Prior Reaction History)||50%||50%|
|False Negative Rate||5%||10-15%|
|Location of Testing||Allergist’s Office||Laboratory|
|Associated Discomfort||Mild, brief discomfort with application followed by 20-60 minutes of itching||Pain and anxiety typical of any blood draw (venipuncture) procedure|
|Stopping Antihistamines Required 7-10 Days Before Testing||Yes||No|
|Time Required to Receive Results||30 minutes||5-7 days|
Additional specialized testing is sometimes needed to confirm or exclude a suspected food allergy when the patient’s history and/or allergy testing results are not entirely conclusive. Carefully designed and closely supervised graded food challenges represent the “gold standard” of food allergy diagnosis. These procedures are performed only in the Medical City Dallas DFAC office, require special scheduling and staffing assignments, and typically take 4-6 hours to complete.