paediatric allergy Flashcards
IgE mediaed allergy pathophys
allergen prested to T cell
B cell activated
bind to mast cells
sensitisation
mast cell exposed to allergen
bursting of mast cell releases inflammatory mediators
exposure to allergen
mast cell degranulation
rapid release and onset of symptoms
histamine, tryptase, hydrolase
later realease of inflammatory mediators - prostaglandins, leukotrienes, cytokines
what does histamine cause
- bronchial smooth muscle contraction
- vasodilation
- separation of endothelial cells (hives)
- pain and itching
genetic influence to allergy
parental atopy (maternal) concordance for allergy in twins
hygiene hypothesis
too clean
children in farmyard environments less allergies/sensitisation
is it allergy?
rapid onset histamine mediated reactions urticaria, erythema, andioedema, pallor/sweating, wheeze improvement with antihistamines relatively quick resolution of symptoms
what caused the reaction?
food environmental allergen drug sting/bite idiopathic
common food allergies
cows milk hen's egg peanuts tree nuts e.g. walnuts soya wheat fish sesame
mild/moderate reaction
angioedema (not involving airway)
urticaria and rash
severe reactions
andioedema of airway (stridor)
bronchospasm
hypotension
supporting evidence that it is an allergy
prev reactions atopy FHx response to Rx co-existing asthma
allergy investigations
skin prick testing
specific IgE - blood test
oral food change
skin-prick testing pros
easy to do
non-invasive
immediate results - 20min
negative SPT very likely not allergy
skin prick testing cons
stop antihistamine 48hrs prior broken skin theoretical risk of reactions dermatographism over-interpretation +ive results avoid random tests
specific IgE pros
no need to stop antihistamines
no risk of reactions
specific IgE cons
expensive invasive delay in obtaining results less sensitive and specific than SPT highly unreliable results in eczema
oral food challenge
day case procedure
gold standard
what actually happens upon contact or ingestion?
invenstigating urticaria and angioedema
urticaria only with no trigger - none, consider SPT/IgE is sus food/environmental trigger
angioedema only - look for hereditary angioedema C4 and C1 esterase inhibitor
rarely: FBC, urinalysis, ESR, LFT, coeliac screen, TFT
treatment of allergies
avoid triggers H1 antihistamine preventative: high dose antihistamines leukotriene antagonist corticosteroids tranexamic acid anti IgE monoclonal antibody (omalizumab) in kids >7yrs
anaphylaxis features
laryngeal oedema hypotension collapse bronchospasm feeling of impending doom onset usually in mins
anaphylaxis onset of symptoms
within 60mins
later the onset the less severe the attack
risk factors for anaphylaxis
poorly controlled asthma stress exercise viral infection alcohol
adrenaline pen
adult 0.3mg, junior 0.15mg
1st line rx anaphylaxis
early use assoc with better outcomes
potential interaction between adrenaline pen and …
b-blockers and tricyclics
adrenaline
reversed peripheral vasodilation inc peripheral vasc resistance improve BP and coronary perfusion decrease angiodema cause bronchodilation dec release inflammatory mediators
who gets adrenaline pen
- suffered severe systemic reaction
- allergen not easily avoidable
- high-risk allergens e.g. nuts with other risk factors e.g. asthma
- reaction to trace amounts trigger
- continuing risk anaphylaxis
- idiopathic anaphylaxis
- signif co-factors e.g. asthma
mangament options
allergen avoidance anti-histamine adrenaline injectors dietary advice optimise asthma control
risk factors for nut allergy
eczema - transcutaneous sensitisation filaggrin mutations eczema creams containing peanut oil egg allergy asthme teenagers and young adults - risk taking, alcohol
oral allergy syndrome
cross reactivity of tree/plant pollens and foods
mainly oral symptoms- itching, mouth swelling, tongue discomfort
peeling or cooking often reduces symptoms
egg allergy
usually mild and benign but can be severe
many grow of it by 5yrs
tolerate well cooked/baked egg first and raw egg last
management of egg allergy
avoidance
re-introduction
egg ladder
IgE mediated cows milk allergy
rapid onset
histamine based reaction
vomiting, occasional diarrhoea
can be identified by SPT or SpIgE
non IgE mediated cows milk allergy
not histamine based
diarrhoea, vomiting, irritable, infantile eczema, bloating, bleeding PR
improves with withdrawal of milk protein
management of IgE mediated cows milk allergy
- maternal avoidance of cow’s milk
- Ca and VitD supplement
- EHF formula
- AA formula if not tolerated
- soya milk >1yr
management of non-IgE CMA
- maternal avoidance of cow’s milk
- Ca and VitD supplement
- EHF formula
- AA formula if not tolerated
- soya milk >1yr
