Paediatric Allergy Flashcards
What are the affects of histamine?
Bronchial smooth muscle contraction
Vasodilation
Separation of endothelial cells
Rash and itching
Describe the genetic influence in atopy?
No parents with atopy = 14% incidence
One parent with atopy= 30%
Two parents with atopy = 60%
What are the characteristics of histamine mediated reactions?
Urticaria Itching Angiodema Pallor/sweating Wheeze Improvement with antihistamines Relatively quick resumption of symptoms
What are the causes of allergy from most to least common?
Food Idiopathic Bee/wasp sting Drugs Exercise (most likely related to a wheat allergy that is exacerbated by exercise)
What are the features of mild/moderate allergic reactions?
Angioedema that spares the airways
Urticaria
Rash
What are the features of a severe allergic reaction?
Angioedema of airways (stridor)
Bronchospasm
Hypotension
How is an anaphylactic reaction characterised?
Characterised by respiratory or cardiac involvement
What supporting features can suggest allergy?
Previous similar reactions Atopy (eczema, hayfever) Family history Response to treatment Co-existing asthma
What investigations can be done for allergy?
Skin prick testing (easy, non-invasive, immediate results, cheap, negative test very likely that no allergy for tested materials)
Specific IgE
Oral food challenge
What are the cons of skin prick testing?
Must stop antihistamines 48hrs prior Shouldn’t be done on broken skin Theoretical risk of reactions Dermatographism Over-interpretation of positive results Avoid random tests
What are the pros of specific IgE testing?
Don’t need to stop antihistamines
No risk of reaction
What are the cons of specific IgE testing?
Expensive and invasive (quite unpleasant for child)
Delay in obtaining results
Less sensitive and specific than skin prick testing
Highly unreliable results in eczema (basal levels of IgE very high in eczema)
What are the features of anaphylaxis?
Laryngeal oedema
Other symptoms
Symptoms begin within 60 mins
20% have biphasic reaction 1-8hrs later therefore need steroids (steroids suppress second reaction not acute reaction) and admission
What are the risk factors for anaphylaxis?
Poorly controlled asthma Stress Exercise Viral infection Alcohol
How are allergies managed?
Advise allergen avoidance Anti-histamines (use non-sedating) Adrenaline injections Dietary advice Optimise asthma control
