Paediatric Allergy Flashcards
Describe mass cell degranulation
Rapid release and onset of symptoms - histamine, tryptase and hydrolase
Later release with subsequent effects - prostaglandins, leukotrienes, PAF and cytokines
What does histamine do?
Most important inflammatory mediator in IgE reaction
Bronchial smooth muscle contraction
Vasodilation - hypotension
Separation of endothelial cells
Pain and itching
What are important features of an allergy?
Rapid onset, histamine mediated reactions, improvement with antihistamines, relatively quick resolution of symptoms and symptoms - urticaria, erythema, angioedema, pallor, sweating and wheeze
What can cause the allergic reaction?
Food, environmental allergen, drug, sting/ bite and idiopathic
What are common food allergies?
Milk, hen’s egg, peanut, tree nut, soya, wheat, fish and sesame
What makes the reaction severe?
Mild/ moderate - angioedema
Urticaria and rash
Severe - angioedema of airway, bronchospasm and hypotension
What are the investigations for allergy?
Skin prick testing, specific IgE and oral food challenge
What are the disadvantages of skin-prick testing?
Must stop antihistamines, broken skin, theoretical risk of reactions, dermatographism, over-interpretation and avoid random tests
Describe specific IgE
No need to stop antihistamines, no risk of reactions, delay in obtaining results, less sensitive than skin prick test and highly unreliable in children with eczema
Describe oral food challenge
Day case procedure
Gold standard
Demonstrates what actually happens upon contact or ingestion
What is the investigation for urticaria and angioedema?
Urticaria only with no trigger then no investigations
Consider SPT and IgE
Angioedema only look for hereditary angioedema - C4 and C1 esterase inhibitor
Rarely - FBC, urinalysis, ESR, LFTs, coeliac screen, TFTs and anti-thyroid Ab
What is the treatment of urticaria and angioedema?
Avoidance of triggers
H1- antihistamines
High dose antihistamines and adding second antihistamine
Leukotriene antagonist, corticosteroids (3-5 days), tranexamic acid and anti IgE monoclonal antibody (Omalizumab)
What is anaphylaxis?
laryngeal oedema, hypotension/ collapse, bronchospasm, feeling of impending doom and onset usually in minutes
What are the clinical features timings?
Almost invariably symptoms begin within 60 mins
Later onset then less severe
20% have biphasic reaction 1-8 hours later - need steroids and hospital admission
What are the risk factors of anaphylaxis?
Asthma, stress, exercise, viral infection and alcohol
Describe the adrenaline pen
Adult 0.3mg/0.5mg and junior 0.15mg
1st line treatment of anaphylaxis
Early use then better outcomes
Interaction possible with BB and tricyclics
What does adrenaline do?
Reverses peripheral vasodilation, increases peripheral vascular resistance, improves BP + coronary perfusion, decreases angioedema, bronchodilation and decreases release of inflammatory mediators
When is adrenaline pen given?
Suffered a severe systemic reaction
Where allergen can not be avoided easily
Allergic to high risk allergens
Continuing risk of anaphylaxis
What is the management for allergies?
Allergen avoidance, anti-histamine, adrenaline pen, dietary advise and optimise asthma control
What are the risk factors for an allergy?
Eczema, filaggrin mutations, eczema creams containing peanut oil, egg allergy, asthma, teenagers and young adults
Describe egg allergy
Most common presentation to allergy clinic in infancy
67% grow out of it
Usually mild and benign
Management - avoidance, reintroduce and egg ladder
Describe IgE mediated cow’s milk allergy
Rapid onset, histamine based reaction, symptoms may vary from vomiting to diarrhoea, and can be identified by SPT or specific IgE
Describe non-IgE mediated cow’s milk allergy
Not histamine based
varying presentations - diarrhoea, irritability, infantile eczema and PR bleeding
No diagnostic tests and dietary management by exclusion
What are different types of milk formulas?
Cow’s milk EHF with/ without lactose, PHF, lactose free formulas, AA and soya/ wheat/ coconut/ almond/ hazelnut
What is the management for IgE:CMA?
Maternal avoidance of cow’s milk
EHF formula
AA formula if not tolerated
Soya milk over 1 year and reintroduction over time
Describe oral allergy syndrome
Cross reactivity of tree/ plant pollens and foods
Causes itching, mouth swelling and tongue discomfort
Antihistamine, avoidance and highly unlikely to cause anaphylaxis
