- Slides: 22
Food Allergy- An Overview Naveena Bobba MD Friday October 23, 2015
Objectives l 1. Understand the presentation of Ig. E mediated food allergy l 2. Identify the appropriate patients to skin test for food allergy l 3. Understand the management of food allergy
Case Study l. GK is an 18 yo M coming in for concerns about food allergy l. Notes that for the last year has had episodes of lip tingling and itching in throat and lips, mainly after eating. Decided to make an appointment because a few weeks ago actually had lip swelling. l. No history of asthma or atopic dermatitis, although thinks his younger brother had eczema as a child, and everyone in the family has hayfever
Food Allergy l. Adverse reactions to food can be categorized as immunologic or non immunologic ¡Food intolerance can include metabolic, pharmacologic, toxic, and/or undefined mechanism l. Food allergy- Adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food ¡Immune responses can be Ig. E or non-Ig. E mediated ¡~13% self report having food allergy, 3% prevalence based on OFC l. Data to suggest that peanut allergy has tripled since late 90's Sampson, H, et al. Food Allergy: A Practice Parameter Update-2014. JACI, 2014; 134(5): 1016 -25.
Adverse Food Reactions
Ig. E mediated food allergy l Includes classic allergic mediated symptoms resulting from exposure of food ¡ Mod-severe Atopic Dermatitis is a significant risk factor food allergy l Diagnosis is clinical, testing can help l Symptoms generally occur within minutes to hours after ingestion l Food allergy is more common in children. l A limited number of foods account for the most significant food allergies: ¡ Milk, egg, soy, wheat, peanut, tree nut, shellfish, fish. l Food allergy more common in people with atopic diseases.
Suspect Food Allergy…. . l In individuals presenting with anaphylaxis or related symptoms that occur within minutes to hours of ingesting food, especially in young children and/or if symptoms have followed the ingestion of a specific food on more than 1 occasion l Most commonly have cutaneous involvement: urticaria, angioedema or erythema ¡ Can also involve GI tract (most commonly vomiting), respiratory system and CV system Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel. JACI, 2010; 126(6): S 1 -58.
History for FA Critical questions should include the following: l What are the symptoms of concern? l What food precipitates the symptoms, and has this food caused such symptoms more than once? l When did symptoms occur in relation to exposure to a given food? l What quantity of food was ingested when the symptoms occurred? l Was the food in a baked (extensively heated) or uncooked form? l Can the food ever be eaten without these symptoms occurring? l Have the symptoms been present at times other than after exposure to a given food? l What treatment was given, and how long did the symptoms last? Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel. JACI, 2010; 126(6): S 1 -58.
Testing for Food Allergy l. Allergy tests yield information on sensitization ¡Indicates presence of food specific Ig. E ¡Testing must be correlated with history and physical exam to determine clinical disease ¡Sensitized patients may tolerate food l False Positive Tests- both skin and blood tests are poorly specific, up to 50 -60% l False Negative Tests- Negative tests occasionally occur in patients with Ig. E-mediated FA. l. Skin test diameter and RAST levels do correlate with likelihood of reaction, but not severity
Positive Predictive Values
Confirming FA l. When skin testing or Ig. E antibody test results do not confirm the clinical history, or the history is not definitive then an oral food challenge (OFC) may be warranted ¡Perform an open oral food l cost- and time-efficient ¡Patient characteristics that increase the risks associated with OFCs include having a history of a previous severe reaction or history of reaction after ingestion of trace amounts of the causal food. ¡Concomitant medical conditions, such as asthma or respiratory tract infection, should be considered before performing OFCs. ¡Delay or defer OFC for those with uncontrolled urticaria or AD
Allergen-Directed Treatment Plans for Food Allergy l. Discussion of avoidance ¡Label reading, cross-contact in food preparation, restaurants ¡For children- work with parents to inform staff in special settings l. Discussion of medical management of anaphylaxis ¡Ingestion is the most likely route for triggering severe allergic/anaphylactic reactions ¡Develop a written action plan for treatment of allergic reactions ¡Indications and technique of self-injectable epinephrine l Practice technique l Ensure Epi pens are accessible and up to date Resources: The Food Allergy & Anaphylaxis Network (www. foodallergy. org); American Academy of Allergy, Asthma and Immunology (www. aaaai. org); American College of Allergy, Asthma and Immunology (www. acaai. org)
Natural History of Food Allergy l Certain food allergies in children can resolve with time ¡Most common in milk, egg, wheat and soy allergies l. Retest yearly to see if sensitization is decreasing ¡Allergy to peanut, tree nut, fish and shellfish are usually more persistent l 20% tolerance to peanut with time, 10% to tree nut l If testing indicates decreased sensitization can consider an OFC ¡If OFC is passed, family should work at incorporating food into diet.
Prevention l No recommendation for mother’s to avoid foods during pregnancy or with breast feeding l Do not delay introduction of foods in infants ¡Increased risk for food allergy or atopic dermatitis- in reference to primary prevention ¡Secondary prevention may need to consider a more cautious approach
A Few Words on LEAP l Randomized infants to early peanut introduction or avoidance ¡Infants were from 4 -6 months old and either had severe eczema or egg allergy l Primary outcome was clinical peanut allergy at 5 years old l Main results: ¡Large reduction in development of peanut allergy in infants randomized to early introduction
LEAP study: Results Du Toit et al, NEJM 2015; 372: 803 -813
Case Study l. GK is an 18 yo M coming in for concerns about food allergy l. Notes that for the last year has had episodes of lip tingling and itching in throat and lips, mainly after eating. l. On further probing this seems to occur with ingestion of apples, melons and peaches. A few weeks ago he was eating a cantaloupe and developed lip swelling l. He does give you a history of rhinitis. When living on the East Coast with his family had symptoms in spring/falltold he was allergic to trees and ragweed. Now has symptoms year long
Oral Allergy Syndrome (OAS) l Oral allergy syndrome is caused by cross-reacting allergens found in both pollen and raw fruits, vegetables, or some tree nuts. l The immune system recognizes the pollen and similar proteins in the food and directs an allergic response to it l OAS most commonly affects patients who are allergic to (specific) pollens (eg, ragweed and birch). Symptoms include pruritus and/or tingling of the lips, tongue, roof of the mouth, and throat with or without swelling. Systemic clinical reactions are rare.
Oral Allergy Syndrome Sampson, H, et al. Food Allergy: A Practice Parameter Update-2014. JACI, 2014; 134(5): 1016 -25.
Take Home Points l The history is critical in the diagnosis of food allergy and is the first step in discerning both the type of food allergy present and the suspected causative food. l Skin testing for food-specific Ig. E is used only in the diagnosis of Ig. E-mediated food allergies. Skin testing is more sensitive than in vitro testing in many cases l Testing in a guide, on occasion a supervised food challenges may required for the definitive diagnosis of food allergy