Paediatric Allergy Flashcards
What is the biphasic reaction of mast cell degranulation?
Rapid release of histamine, tryptase and hydrolase and onset of symptoms
Later release of inflammatory mediators prostaglandins, leukotrienes, PAF, cytokines
What is the effect of histamine?
Bronchial smooth muscle contraction
Vasodilation
Separation of endothelial cells leading to hives (urticaria)
Pain and itching
What are some characteristics of an allergic reaction?
Rapid onset
Histamine mediated reactions
Improvement with antihistamines
Relatively quick resolution
What are the main groups of allergies?
Food Environmental Drug Sting/bite Idiopathic
How do we investigate allergy?
Skin prick testing
Specific IgE
Oral food challenge
What are some pros of skin-prick testing?
Easy to perform
Non-invasive
Immediate results
Cheap
What are some drawbacks to skin-prick testing?
Must stop antihistamines 48hrs prior Broken skin Theoretical risk of reactions Dermatographism Over-interpretation of positive results Avoid random test
What are some pros for specific IgE testing?
No need to stop antihistamines
No risk of reactions
What are some drawbacks of specific IgE?
Expensive and invasive
Delay in obtaining results
Less sensitive and specific than SPT
Highly unreliable results in eczema
What would be a reasonable specific IgE concentration result for egg, milk and peanut allergies?
Egg - 7
Peanut - 14
Milk - 15
What is oral food challenge?
Gold standard
What actually happens upon contact or ingestion
What are some genes associated with angioedema?
Hereditary angioedema C4 and C1 esterase inhibitor
Name some good 2nd/3rd generation antihistamines
Fexofenadine (allegra)
Loratidine (claritin)
Cetirizine (zyrtec)
What is the main difference between 1st and 2nd generation antihistamines?
2nd generation mainly just block histamine receptors and not muscarinic
2nd generation do not cross the BBB
What are some features of angioedema?
Laryngeal Oedema Hypotension/collapse Bronchospasm Feeling of impending doom Onset usually in minutes
What are some risk factors for anaphylaxis?
Poorly controlled asthma Stress Exercise Viral infection Alcohol
What is the first line treatment for anaphylaxis?
Adrenaline pen
What are some effects of adrenaline?
Reverses peripheral vasodilation Increases PVR Improves BP Decreases angioedema Bronchodilation Decreases inflammatory mediators
How do we manage food allergies?
Avoid allergen Anti-histamine Adrenaline injectors Dietary advice Optimise asthma control
What are some risk factors for nut allergies?
Eczema Filaggrin mutations Eczema creams containing peanut oil Egg allergy Asthma
What is oral allergy syndrome?
Cross reactivity of tree/plant pollens and foods
Mainly oral symptoms
How might non-IgE mediated cow’s milk allergy present?
Diarrhoea Vomiting Irritability Infantile eczema Bloating PR bleeding
