Transcript Food Allergy

Food Allergy- An Overview
Naveena Bobba MD
Friday October 23, 2015
Objectives
1. Understand the presentation of IgE
mediated food allergy
2. Identify the appropriate patients to skin
test for food allergy
3. Understand the management of food
allergy
GK is an 18 yo M coming in for concerns about food
allergy
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.
No history of asthma or atopic dermatitis, although
thinks his younger brother had eczema as a child,
and everyone in the family has hayfever
Adverse reactions to food can be categorized as
immunologic or non immunologic
Food intolerance can include metabolic, pharmacologic,
toxic, and/or undefined mechanism
Food allergy- Adverse health effect arising from a
specific immune response that occurs reproducibly
on exposure to a given food
Immune responses can be IgE or non-IgE mediated
~13% self report having food allergy, 3% prevalence
based on OFC
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
IgE mediated food allergy
 Includes classic allergic mediated symptoms resulting
from exposure of food
 Mod-severe Atopic Dermatitis is a significant risk factor for food
allergy
 Diagnosis is clinical, testing can help
 Symptoms generally occur within minutes to hours after
ingestion
 Food allergy is more common in children.
 A limited number of foods account for the most
significant food allergies:
 Milk, egg, soy, wheat, peanut, tree nut, shellfish, fish.
 Food allergy more common in people with atopic
diseases.
 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
 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):S1-58.
Critical questions should include the following:
 What are the symptoms of concern?
 What food precipitates the symptoms, and has this food caused
such symptoms more than once?
 When did symptoms occur in relation to exposure to a given food?
 What quantity of food was ingested when the symptoms occurred?
 Was the food in a baked (extensively heated) or uncooked form?
 Can the food ever be eaten without these symptoms occurring?
 Have the symptoms been present at times other than after
exposure to a given food?
 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):S1-58.
Allergy tests yield information on sensitization
Indicates presence of food specific IgE
Testing must be correlated with history and physical
exam to determine clinical disease
Sensitized patients may tolerate food
False Positive Tests- both skin and blood tests are poorly
specific, up to 50-60%
False Negative Tests- Negative tests occasionally occur in
patients with IgE-mediated FA.
Skin test diameter and RAST levels do correlate
with likelihood of reaction, but not severity
When skin testing or IgE 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
 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
Discussion of avoidance
Label reading, cross-contact in food preparation,
restaurants
For children- work with parents to inform staff in special
settings
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
 Practice technique
 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
 Certain food allergies in children can resolve
with time
Most common in milk, egg, wheat and soy allergies
Retest yearly to see if sensitization is decreasing
Allergy to peanut, tree nut, fish and shellfish are
usually more persistent
20% tolerance to peanut with time, 10% to tree nut
 If testing indicates decreased sensitization can
consider an OFC
If OFC is passed, family should work at incorporating
food into diet.
Prevention
No recommendation for mother’s to avoid
foods during pregnancy or with breast
feeding
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
Randomized infants to early peanut
introduction or avoidance
Infants were from 4-6 months old and either
had severe eczema or egg allergy
Primary outcome was clinical peanut
allergy at 5 years old
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
GK is an 18 yo M coming in for concerns about food
allergy
Notes that for the last year has had episodes of lip
tingling and itching in throat and lips, mainly after
eating.
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
He does give you a history of rhinitis. When living on
the East Coast with his family had symptoms in
spring/fall- told he was allergic to trees and ragweed.
Now has symptoms year long
Oral Allergy Syndrome (OAS)
 Oral allergy syndrome is caused by cross-reacting
allergens found in both pollen and raw fruits,
vegetables, or some tree nuts.
 The immune system recognizes the pollen and
similar proteins in the food and directs an allergic
response to it
 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
 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.
 Skin testing for food-specific IgE is used only in the
diagnosis of IgE-mediated food allergies. Skin
testing is more sensitive than in vitro testing in many
cases
 Testing in a guide, on occasion a supervised food
challenges may required for the definitive diagnosis
of food allergy
Questions????