Paediatric Allergies Flashcards
Definition of an allergy
Allergen specific reproducible immune mediated hypersensitivity reaction
Definition of sensitisation
Production of IgE antibodies after repeated exposure to an allergen
Definition of atopy
A tendency to produce IgE antibodies in response to ordinary exposure to potential allergens
Associated with asthma, rhinitis, eczema and food allergy
Anaphylaxis
Rapid, life threatening hypersensitivity response to an allergen
Investigations for suspected allergy
Screening:
- Skin prick test - low sensitivity therfore used to rule out allergy
- Blood specific IgE - useful to confirm diagnosis
- Elimation from diet
Diagnosis verification:
- controlled oral food challenge
Allergy history (EATERS)
Exposure - eaten, smells, handling
Allergen - common food allergens
Timing - IgE mediated - immediate, non IgE mediated - delayed
Environment - weaning, eating away e.g. holiday or nursery
Reproducibilty - no reaction if avoiding the food
Symptoms - rash, nausea and vomiting, breathlessness, angioedema
FHx
Skin symptoms
Pruritis
Erythema
Urticaria
Angioedema - lips, face and around eyes
GI symptoms
Nausea and vomiting
Diarrhoea
Colickly abdominal pain
Respiratory symptoms
Blocked or runny nose Sneezing Itch Wheeze Cough Breathlessness
Cardiovascular symptoms
Pallor
Drowsy
Hypotension
Non IgE mediated specific symptoms
Atopic aczema
Food refusal
GORD - not responding to treatment
Constipation
Cross reactive food allergens
If allergic to on allergen, more likely to be allergic to another similar allergen e.g. cow’s milk and goats milk
Which type of sensitivity reaction is a food allergy
Type 1
Pathophysiology of allergy
- Sensitisation - allergen presented to T cell
- TH2 cells commit B cells to produce IgE
- Allergen specific IgE bind to mast cells and basophils
- Subsequent allergen exposure in sensitised patient
- Allergens cross link receptor bound IgE which activates mast cells and bosphils
- Mast cells release mediators - cytokines and leukotrienes
Immunoassay of serum IgE method
- Allergen absorbed onto a solid phase
- Patients serum is added
- Allergen bound IgE detected using a IgE monoclonal antibody - detects IgE circulating in the blood
How does a skin prick test work?
Skin prick test exposes the patient to the allergen
Detects IgE bound to skin mast cells
Wheal size
More than 8mm has a 95% positive predictive value
Do levels or allergy testing correlate with severity
No
- determines presence of sensitivity
Cows milk protein allergy presentation
General:
- irritable, crying and poor sleep
- atopy
Feeding:
- difficult to feed
- vomiting and pulls legs up
- back arching or abdo pain
Bowels:
- constipated or loose stools
- straining
- mucus/ blood in stool
- vomiting
- bloating
Skin:
- erythema
- Pruritis
- urticaria
- angioedema
Differentials for CMPA
GORD
Pyloric stenosis
Hirschprung disease
Malrotation
Features of CMPA
All present before 12 months old
Delayed response - weeks
Most become tolerant by the age of 5 yo
FPIES - food protein enterocolitis syndrome features
- Non IgE mediated food hypersensitivity
- Presents in infancy
- Delayed presentation 1 - 3 hours after exposure
FPIES presentation
Rectal bleeding
Profuse repetitive vomiting leading to shock
Pallor
CRP NORMAL, WCC elevated
Management of CMPA
Breastfeeding:
- mother to avoid milk in diet if exclusively breastfeeding
- give mother calcium and vitamin D
Not breastfeeding:
- trial of extensively hydrolysed formula
- if not tolerated, amino acid formula
- soya infant formula if > 6 months
Administration of adrenaline
- Lie child flat with legs raised or sit up
- Inject adrenaline in lateral thigh
- Time, if symptoms not resolved after 5 mins, inject again
Rhinitis
Inflammatory disorder of the nasal mucosa initiatedd by an allergic immune reaction to inhales allergens
Rhinitis presentation
Nasal congestion Rhinorrhoea Sneezing Itching Mouth breathing Halitosis - bad breath Allergic facies Swollen nasal turbinates
Allergic facies
Lick eczema - due to dry lips Swollen midface Mouth breather Allergic crease (nose) Allergic shiners - eye bags
Management of rhinits
Intranasal corticosteroids - beclomethasone
Oral antihistamine - cetirizine (non sedating)
Intranasal decongestants
Anaphylaxis management
- IM 1:1000 Adrenaline - repeat after 5 mins if still symptomatic
- 12+ yo - 500 micrograms
- 6 - 12yo - 300 micrograms
- 6 months - 6 years - 150 micrograms
Top 3 common allergens in children
Cow’s milk
Tree nuts
Eggs
Types of hypersensitivity reactions and examples
Type 1 - IgE mediated - allergies
Type 2 - IgG and IgG - haemolytic anaemia and transfusion reactions
Type 3 - immune complexes - Henoch Schonlein purpura, SLE, RA
Type 4 - T lymphocytes - contact dermatitis
What needs to be stopped before a skin prick test is done
Antihistamines
Management of anaphylaxis after the reaction
- Period of observation due to biphasic reactions
- serum mast cell tryptase within 6 hours of reaction
- education and follow up
Triggers for allergic rhinitis
Pollen
House dust mites
Pets
Mould
Nasal spray technique
Close one nostril and spray in other
Spray upwards and then sniff (not at same time)
Should not be able to taste medication
