JC116 (Paediatrics) - Eczema and food allergies in children Flashcards
Conditions that define Atopy
Food allergy
Atopic eczema
Asthma
Rhinoconjunctivitis
Age for peak incidence of atopic conditions
Allergic dermatitis and food allergy = 1-3 years old
Asthma = 4-9 years old
Rhinoconjunctivitis = Incidence increase with age
Pathogenesis of atopic dermatitis
- Mutation in flaggrin + skin scratching > skin barrier becomes easily disrupted
- antigens/ allergens bind to Langerhan cells > present to T- helper cells for Th2 response > IL-4 activate eosinophils and Macrophage, B cells also class-switch into IgE producing and activation of mast cells
- Increased E-selectin, VCAM-1, and ICAM levels increase itchiness and worsen disruptive cycle
- Introduce microbes into skin and worsen inflammatory response
- Chronic atopic dermatitis with acute flares
Triggers of atopic dermatitis
Foods (IgE-induced) & those having vasodilatory properties: egg, milk, peanut
Irritants:
Wool
Soaps/ detergents, disinfectants
Occupational dusts, tobacco smoke
Climate: xerosis (dry skin), heat/ sweating
Aeroallergens: grass, Alternaria alternata (fungus)
Microbial agents: S. aureus, viral infection, ?dermatophytes
Contactants (incl. house dust mites, cat)
Psychological and Hormones
Atopic conditions associated with atopic dermatitis
50-60% of patients develop respiratory “allergies”
80% of occupational skin disease occur in atopics
Food allergies
List food a/w allergy
Milk, egg
soy, wheat
nut products
fish/ shellfish
Pathophysiology of food allergy
Food start cutaneous non-eczematous and eczematous responses via:
- A rise in plasma histamine
- Activation of eosinophils;
- Clonal expansion of allergen-specific skin homing T-cells
Biphasic response in the skin
Acute pruritic lesions»_space;> Eczematous lesion after cellular infiltration
Diagnostic investigations for atopic dermatitis
History and physical examination (Mainstay of Dx)
Laboratory (never routine):
Serum IgE level
Serum test for allergen-specific IgE (CAP-RAST)
Skin biopsy
Skin culture (bacterial, viral, fungal)
Atopy patch test (corticosteroids, aeroallergens)
Skin prick test (never routine)
Complications of atopic dermatitis
Secondary infections:
- S. aureus infection»_space;> Impetiginization
- Viral infections:
Local: Verruca, molluscum, herpes
Systemic: Kaposi’s herpetiform eruption
- Mycotic infection: Dermatophytes, candida
Psychological distress:
- Poor sleep, absence from school
- Stress, disruption of family life
Failure to thrive
Treatment for refractory atopic dermatitis
Topical Calcineurin inhibitor with adjunctive therapy
Treatment options for atopic dermatitis
short-term and long-term control
- Prevent and reduce flares
- Avoid irritantants and triggers
- Emollients and bath oils
- Wet warp dressings - Improve long-term control
- Antibiotics
- topical steroids (adjusted dose to severity**)
- Systemic immunosuppression - Improve sleep and QoL
- Sedative antihistamines
Treatment options for atopic dermatitis
- Prevent and reduce flares
- Avoid irritantants and triggers
- Emollients and bath oils
- Wet warp dressings - Improve long-term control
- Antibiotics
- topical steroids (adjusted dose to severity**) - Improve sleep and QoL
- Sedative antihistamines
Function of wet wrap dressings for atopic dermatitis
Rehydration and cooling of skin
Reduce itchiness
Prevent scratching
Enhance absorption of topical steroid ointment, reduce total dose of topical steroids
Systemic therapy options for long-term control of atopic dermatitis
Steroids Azathioprine Cyclosporin A Mycophenolate mofetil Methotrexate
Generally Immunosuppressants not advised due to unnecessary immunosuppression
Oral steroid rarely used due to fast recurrence after withdrawal
Food allergy
- Define
- Difference with food intolerance or food aversion
Food allergy: form of food intolerance associated with a hypersensitive immune response. Systemic response manifests as eczema, asthma and allergic rhinitis
Food intolerance = reproducible reaction to a food/ food ingredient which occurs in a Double-blind placebo controlled food challenge (DBPCFC)
Food aversion = bodily reaction caused by food which cannot be reproduced by DBPCFC
risk factors for food allergy:
Genetic predisposition to specific food allergy or atopy
Immunological: Atopic dermatitis
Environmental
Maternal ingestion during pregnancy or breastfeeding
Dietary & environmental exposures: ingestion, topical exposures
Use of antacids
Manner of food processing
Systemic manifestations of food allergy
Skin: Urticaria, angioedema, eczema
Respiration: Rhinitis, asthma
GI: diarrhea and vomiting, eosinophilic gastroenteritis, enterocolitis
CNS: migraine, hyperactivity, sleep disturbance
General: Failure to thrive
Most common triggers of anaphylaxis in children in HK
Food = no.1 trigger of anaphylaxis
- Shellfish, fish and seafood
- Cow’s milk, diary products
- Hen’s eggs
- Peanuts and tree nuts
- Miscellaneous: legumes, fruits, muschrooms….etc
3 pathophysiological mechanisms of food allergy
Diagnostic tests for each mechanism
IgE-mediated (immediate onset, oral allergy syndrome)
- Skin prick test
- Serum specific IgE with CAP-RAST system
Cell-mediated/ non-IgE mediated (delayed onset)
- double-blind placebo-controlled food challenge
- Elimination challenge
(Under research: Patch test, in-vitro cellular markers and flow study)
Mixed type (most common) - Clinical Dx
Management options for food allergy
Intramuscular Epinephrine (adrenaline)
Desensitization therapy
Anti-IgE therapy
Define epipen dosages for children and adults
Indicators of Epipen use
Dosage:
Children 10-20kg - 150 microgram
Children over 20kg and adults - 300 micrograms
Indicators:
- Airway obstruction and breathing difficulty
- Hypotension
- Loss of consciousness and muscle tone
