به نام خدا. management of food allergy adverse reactions to foods food intolerance (most...
TRANSCRIPT
خدا نام به
MANAGEMENT OF FOOD ALLERGY
By:
TOOBA MOMEN
Clinical Allergist & Immunologist
ADVERSE REACTIONS TO FOODS
Food intolerance (most common)
Food allergy (hypersensitivity)
Food aversion (phobia)
FOOD INTOLERANCE
It caused by factors inherent in food ingested:
Enzyme Deficiency
GI disorders
Anatomical defect
Physiological effects of Active Substances
Food Additives & Contaminants
Neurologic disorder
FOOD ALLERGY
An adverse health effect arising from a
specific immune that occurs on exposure to a
given food
E P I D E M I O L O GY O F F O O D A L L E R GY
Food allergy is on the increase in developed countries
Factors contributing to the epidemic appear to be related to
the modern lifestyle but as yet are poorly understood.
The incidence of food allergy-related anaphylaxis, the most
severe consequence of food allergy, is rising particularly in the
under 4-year age group.
Overall more than 90% of food allergies in children are caused
by cow’s milk, hen’s egg, soybean, wheat, peanut, tree nut, fish,
and shellfish. → overall 8%
In adults sea food( 2.3%), peanut& tree nut(1.2%) → overall
3.5-4 %
FREQUENTLY ALLERGENIC FOODS
Most common food allergies
in young children: Milk (casein, whey) Eggs Wheat (gluten) Soy Peanuts Tree nuts Shellfish
Most common food allergies
in older children & adults Fish Shellfish Peanuts Tree nuts
PATHOPHYSIOLOGIC MECHANISMS OF FOOD ALLERGY
In the susceptible host, a failure to develop or a breakdown in oral tolerance, commonly a result of heavy occupational exposure or sensitization to cross-reactive allergens may result allergic responseIgE mediated
Non IgE mediated
Mixed IgE & non IgE mediated
Immediate <1 hour
Delayed >24 hours
Volume required for reaction
Class IgE mediated
Non-IgE mediated
Time to onset of reaction
Immediate<1 hour
Delayed>24 hours
Volume required forreaction
Small (e.g. <10 ml) Large (e.g. >100 ml)
Symptoms/ syndromes
Urticaria, angioedema,vomiting, anaphylaxis,oral allergy syndrome,eczema
Diarrhoea, eczema, failure to thrive, gastrooesophageal Reflux,food proteininduced enteropathy, enterocolitis and proctocolitis, multiple food allergy
Diagnosticprocedures
Above signs or symptoms byhistory or oral food challengeAND positive IgE antibodies(skin prick test or cap-FEIA)
Home based elimination andRechallenge sequence (no riskof anaphylaxis
MANIFESTATIONS OF FOOD ALLERGY
CUTANEOUSIgE mediated:
Urticaria, Angioedema
Contact urticaria
Mixed IgE &non IgE mediated:
Atopic dermatitis
Non IgE mediated:
Contact dermatitis
Dermatitis herpetiform
GASTROINTESTINLIgE mediated:
Acute gastrointestinal hypersensitivity
pollen-food allergy syndrome
IgE & non IgE mediated:
Eosinophilic esophagitis
Allergic eosinophilic gastroenteritis
Non IgE mediated:
Allergic proctocolitis
food protein induced entrocolitis
food protein induced enteropathy,
celiac
RESPIRATORYIgE mediated
Allergic rhinoconjuctivitis
Allergic bronchospasm
IgE & non IgE mediated:
Asthma
Non IgE mediated
Pulmonary hemosiderosis
DIAGNOSIS & MANAGEMENT OF FOOD ALLERGY
HISTORY &PHYSICAL EXAMINATION
Food presumed to have provoked the reaction
Quantity of the suspected food ingested
Length of time between ingestion &development of symptoms
Whether similar symptoms developed on other occasions when the food was
eaten
Whether other factors (exercise, alcohol, drugs) are necessary
How long since the last reaction to food occurred
Personal hx of atopy
Family hx of food allergy & atopy
Diet diaries
DIAGNOSTIC TEST
SKIN PRICK TEST
Skin prick or puncture tests to foods are very useful when properly performed and interpreted.
Negative prick/puncture skin tests have a high negative
predictive accuracy for many foods (>95% for the common foods). Positive prick/puncture skin tests have a high
positivepredictive accuracy for egg, milk and peanut in youngchildren, and the size of the skin test is relativelypredictive. A negative test with a suspicious history requires afood challenge before the food is returned to the diet
INVITRO TEST FOR SPECIFIC IGE
Food specific IgE exceeding the diagnostic values indicate that
patients are more than 95% likely to experience allergic reaction
after ingestion of specific food
PREFERENCE FOR IN VITRO TESTS VS SKIN TESTS
Patients with extensive dermographia
Patients with extensive atopic dermatitis or generalized urticaria
Patients who cannot discontinue antihistamines
Areas where there are no allergists to perform skin testing
ORAL FOOD CHALLENGE PROCEDURES
Oral food challenges (particularly double-blind placebo-
controlled food challenge) represent the accepted gold
standard investigation for objective diagnosis of both
immediate and delayed-onset food allergy.
Oral food challenges are clinically indicated to
demonstrate allergy or tolerance to achieve safe dietary
expansion or appropriate allergen avoidance
20
CHALLENGEDouble-blind Placebo-controlled Food Challenge (DBPCFC)
• Freeze-dried food is disguised in gelatin capsules• Identical gelatin capsules contain a placebo (glucose
powder)• Neither the patient nor the supervisor knows the
identity of the contents of the capsules• Positive test is when the food triggers symptoms
when the placebo does not
21
CHALLENGE CONTINUED
Single Blind Food Challenge• Supervisor knows the identity of the food• Food is disguised in strong-flavoured food e.g. apple
sauce; lentil soup
Open Food Challenge• Sequential incremental doe challenge (SIDC)• Determines sensitivity and dose tolerated for each eliminated food
in its purest form
INDICATION FOR OFCIndication Rationale
Demonstrate tolerance
1. Allergy suspected to have been outgrown, e.g. the child who was previously eggallergic but now returns ever-decreasing allergy test results.2. When the food has been tolerated in some presentations but not others e.g. baked egg in cakes tolerated but scrambled egg causes a reaction.3. When allergy tests suggest tolerance, but food never eaten and patient and/orparent too cautious to introduce at home.4. Cross-reactivity suspected, e.g. the child with a low positive IgE result to wheat but high positive grass pollen sensitization.5. When the diet is restricted due to a suspicion that one or more foods is resulting in delayed allergic symptoms, e.g. eczema, gastroesophageal reflux.6. To establish a tolerance threshold to allergen proteins (currently restricted to theresearch setting).7. When multiple dietary restrictions are maintained but symptoms are subjective.
Demonstrate allergy 1. Suspected food allergic reaction but cause uncertain despite SPT and Sp-IgE testing,
2. Suspected food allergic reaction but equivocal or inconsistent symptoms following consumption of a particular food
Monitor therapy for food allergy
To monitor response to immunomodulatory treatment in the research setting.
INDICATIVE OF IGE MEDIATED
Skin prick test, and or food specific IgE
Negative
Reintroduction of food into diet; If convincing history of anaphylaxis consider OFC
Positive
Convincing h/o allergic reaction
NOConsider OFC and reintroduction of
food
YESStrict dietary food
avoidance; nutritional support
Periodic reassessment; if specific IgE is detectable,
reintroduction should be done as OFC
I N D I C AT I V E O F C E L L M E D I AT E D O R M I X E D M E C H A N I S M
Biopsy, Serologic test for Celiac, Peripheral Eosinophil, ,Stool for
occult Blood, Hb, Albumin, Total protein
Consider skin prick test or Specific IgE
Trial of Elimination Diet, foods selected based on experience
&result of screening test; if food specific IgE is detectable OFC may
be done for reintroduction
Resolution
NOReview diet &
reconsider food. Correct diagnosis?
YesStrict diet
FOOD ALLERGEN AVOIDANCE STRATEGIES
Should be prescribed based on confirmed diagnosis
Some times strict avoidance in not necessary
-extensively heated product for egg or milk allergy
- maternal ingestion of allergen while breast
feeding
- raw fruit & vegetables causing oral symptoms
Labeling of manufactured product
Cross contact
LABELING
MANNER OF EXPOSURE
Skin contact
Inhalation
Ingestion
EXAMPLES OF FOOD ALLERGENS IN UNEXPECTED AND NONFOOD ITEMS
Cosmetics almond or milk in shampoos or ointments
Pet food milk, egg, fish, soy
Medications lactose in DPI or tablet , soy lecithin
Vaccines egg(influenza, yellow fever), milk(DPT)
Nutrition supplements glucosamine chondrotin
supplements(shark cartilage or shrimp shell)
Saliva(kissing) residual protein from meals
Transfusion containing allergen from donor ingestion
N A T U R A L H I S T O R Y O F F O O D A L L E R G Y
Most young children outgrow their food
sensitivity within a few years except in
most cases of peanut, tree, and seafood
Milk Allergy:
most of them become tolerant till 3y/o, 50% by 1y/o,
70% by 2 y/o, 85% by 3 y/o
Egg Allergy:
66% become tolerant by 5 y/o
Peanut Allergy: 20% become tolerant with age
Tree nut Allergy : 9% become tolerant with age
EMERGENCIY MANAGMENT
Prompt recognition of reaction
Treatment with epinephrine and antihistamines
Emergency plans and special considerations for schools
FOOD ALLERGY PREVENTION
C H A N G E S I N N O T I O N S A B O U T A L L E R G Y P R E V E N T I O N T H R O U G H D I E T
Prior notion/recommendation for those at risk for atopy
Recent notion
Avoid peanut during pregnancy No proof of effectiveness
Avoid food allergens during lactation Possible reduction in eczema, no evidence regarding food allergy
Exclusive breast feeding for 3-4 months
May protect for atopy, but evidence is modest, lack of evidence for food allergy prevention
Alternative hypoallergenic formula May protect for atopy, but evidence is modest, lack of evidence for food allergy prevention
Delay complementary foods until 4-6 months
Lack of evidence to prevent atopic disease
Avoid allergens: milk to 1y/o, egg to 2y/o, and peanut, nut , and fish to 3 y/o
Early introduction of allergenic foods at 4-6 m/o may protect against development of food allergy, but firm evidence is lacking
F U T U R E T H E R A P E U T I C S T R A T E G I E S
Strict avoidance of allergens is not curative and
leaves patients
at risk for accidental exposure. As such, several new
therapeutic
approaches are being tested in clinical trials.
ALLERGEN NON SPECIFIC THERAPIES
Humanized monoclonal anti- IgE
Traditional Chinese Medicine
Probiotics &Prebiotics
ALLERGEN SPECIFIC IMMUNOTHERAPY
Oral immunotherapy
Extensive heated milk & egg proteins
Sublingual Immunotherapy
Epicutaneous Immunotherapy
Modified or recombinant allergen immunotherapy
SUMMARY
Current therapy for food allergy requires
education about avoidance in a variety of setting &
instruction on when &how to treat inevitable allergic
reactions
Current therapeutic strategies are focused on
harnessing oral tolerance to modulate allergic
response using Ag-specific & non specific
approaches.
THANK YOU FOR YOUR ATTENTION