This document discusses food allergies, including: - Common food allergens in adults and children and different types of food-related diseases. - The diagnosis of food allergy is challenging due to limitations of diagnostic techniques. - Treatment involves avoiding problematic foods based on an accurate diagnosis, using emergency medicines like epinephrine for reactions, and having a written emergency plan.

1. ALLERGIES DUE TO
FOOD

2. Learning Objectives
• At the end of this presentation you will be able
to:
• Recognise the main pathogenic food allergens in
adults and children
• Differentiate between IgE-mediated,cell
mediated and mixed IgE- and cell mediated food
related diseases in different organ systems
• Discuss the diagnosis of food allergy and the
limitations of diagnostic techniques
• Review the treatment of food allergy

3. Definition of Allergy due to Food
• Any abnormal clinical response attributed to
ingestion ,contact or inhalation of any food, a
food derivative or a food additive
• TOXIC
• NON TOXIC OR HYPERSENSITIVITY

4. Adverse reactions to Food
• Toxic
• Nontoxic
Immune Mediated
Allergy
Non IgE mediated
IgE mediated
• Non Immune Mediated
Intolerence
• Enzymatic
• Pharmacologic
• Undefined
•

5. Prevalence & causes of food allergy
• Precise prevalence is unknown, but estimates
are:
• Adults; 1.4% -2.4%
• Children less than 3 years:6%
• Atopic dermatitis (mild/severe):35%
• Asthmatic children:6-8%
• Prevelance depends on:genetic factor,age,dietary
habits,geography and diagnostic procedures

6. Pathophysiology:Allergens
• Protein (not fat/carbohydrate)
• -10 -70kD glycoprotein
• -Heat resistant,acid stable
• Major allegenic foods(less than 85% of allergy)
• -Children:milk,egg,soy,wheat other depending on
geographical area
• -Adults:peanut,nuts,shellfish,fish
• Single food(or related) greater than many food allergies
• Characterisation of epitopes underway
• -Linear vs conformational epitopes
• B cells vs T cells epitopes

7. Food Allergens
• Class 1 food allergens
• Primary sensitizers
• sensetization may occur through the GIT
• water soluable glycoprotein
• Molecular weights ranging from 10 to70kD
• Stable to heat,acid and proteins
• Class 2 food allergents
• Generally plant derived proteins
• Highly heat labile
• Difficult to isolate
• No good,standarized,extracts are available for diagnostic
purposes

8. Pathogenesis of food hypersensitivity
gut barrier
• The immune system associated with this barrier is
capable of discriminating among harmless foreign
proteins or commensal organisms and dangerous
pathogens
• Food allergy is an abnormal response of the
mucosal immune system to antigen delivered
through the oral route
• The immune state of the mucosal barrier and
immune systems might play a role in the increased
prevalence of gastointestinal infections and food
allergy in the first few years of life

9. • About 2% of ingested food antigen are
absorbed and transported throughout the
body in an immunological intact form ,even
through the immature gut
• The underlying immunological mechanisms
involved in oral tolerence induction have not
been fully elucidated

10. Cutaneous food hypersensitivities
• Acute Urticaria and Angioedema:
• The most common symptoms of food alleric
reactions
• The exact prevalence of these reactions is
unknown
• Acute urticaria due to contact with food is also
common
• Chronic Urticaria:
• Food allergy is an anfrequent causes of chronic
urticarian and angioedema

11. Ig E mediated : respiratory
manifestations
• Asthma
• An uncomman manifestation of food allergy
• Usually seen with other food-induced symptoms
• Vapours or steam emitted from cooking food may induced
asthmatic reaction
• Food induced asthmatic symptoms should be suspected in
patients with refractory asthma and history of atopic
dermatitis ,gastroesophagal reflux , food allergy or feeding
problems as an infant, or history of positive skin tests or
reactins of food
• Rhinoconjuctivitis
• Usually seen durind positive controlled challenge tests, but
occasionally reported by patients

12. IgE Mediated : systemic reaction
anaphylaxis/anaphylaxis syndrome
• Food induced anaphylaxis
• -Rapid onset
• -Multi organ system involvement
• -Potentially fatal
• -Any food, highest risk:
• peanut,nut,seafood,milk,egg
• Food dependent- exercise-induced
• Associated with a particular food
• Associated with eating any food

13. Fatal food anaphylaxis
• Frequency- 100 deaths/yr
• Risk
• Underlying asthma
• Symptom dental
• Delayed epinephrine
• Previous severe reaction
• History :known allergic food
• Biphasic reaction
• Lack of cutaneous symptoms

14. Treatment :avoidance
• Mainstay of treatment
• Must be considered as a therapeutic approach
• Risk - benefit must be assessed
• -correct diagnosis is essential
• -Very restictive diets can lead to
malnutrition
• Dietician’s role is crucial

15. Food allergy :treatment
• Correct diagnosis
• Treatment of reactions
• Avoidance
• Role of dietician
• Tolerance assessment
• Prevention
• Immunotherapeutic strategies

16. Treatment emergency medicines
• Epinephrine:drug of choice for reactions
• -Self –administered epinephrine readily available
• -Train patients :Indications/technique
• Antihistamines:Secondary therapy
• Emergency plan in writing
• -schools,spouses,caregivers,mature
siblings/friends
• Emergency identification bracelet

17. Thank You