allergy Flashcards
describe the pathophysiology of an IgE mediated
rapid release of:
histamine, Tryptase, Hydrolase
-rapid onset of symptoms
LATER imflammatory mediators released: prostaglandins, Leukotrines, PAF, Cytokines
effect of histamine?
- bronchial smooth muscle contraction
- Vasodilation
- Seperation of endothelial cells (resp for hives)
- Pain and itching
what is the genetic influence towards allergy and atopy
maternal atopy
concordance for allergy in twins
no parent: 14%
one parent:30%
2 rents: 60%
hygiene hypothesis
what is an allergy reaction?
IgE mediated
features of an allergy?
rapid onset histamine mediated Urticaria Erythema angiodema Pallor/sweating wheeze Improvement with anti histamines relative quick resolution to symptoms
what are common food allergens?
milk allergy hen's egg tree nuts soya fish sesame wheat
what makes an allergy mild?
mild to moderate:
angiodema (not involving airway)
urticaria and rash
what makes an allergy severe?
angiodema of airway (causing stridor)
bronchospasm
hypotension
what investigation should you do if you suspect an allergy?
skin prick testing
specific IgE
Oral food challenge
pros and cons of skin prick testing?
pros: easy to perform non invasive cheap immediate results- in 20 mins
cons: stop antihistamines 48 hours beforehand broken skin theoretical risk of reaction dermatogiphsm over interpretation of positive results avoid random tests
specific IgE pro’s and cons:
pro's: No need to stop antihistamines no risk of reaction expensive and invasive less sensitive and specific than SPT highly unreliable results in eczema
what is the gold standard test for allergy?
oral food challenge
when to do each tests?
just urticaria- none
suspected food allergy- SPT
angiodema only- (most common in teens with new presentation)look for C4 and C1 esterase inhibitor
allergy treatment?
allergy avoidance
H1 antihistamine (2nd/3rd gen)
high dose antihistamine +/- amntihistamine
leukatrine antagnost
CCS (3-5 days)
tranexamic axid
anti IgE antibody (omalizumab) in children over 7
anaphylaxis features?
laryngeal oedema hypotension/collapse bronchospasm feeling of impending doom onset usually in minutes
almost invariable symptoms begin in 1 hour
RF for anaphylaxis?
asthma (poorly controlled) stress exrecise viral infection alcohol
how much adrenaline in an epipen? adult vs kid?
adult: 0.3mg
kid: 0.15mg
what does adrenaline do in an anaphylactic reaction?
decrease angiodema reverse peripheral oedema increase peripheral vascular resistance causes brachiodilation decreases release of inflame mediators improves BP and coronary perfusion
RF for peanut allergy?
eczma Filaggrin mutation Eczema creams containing peanut oil egg allergy asthma teens and young adults-risk taking, alcohol
what is oral allergy syndrome?
kid allergic to fruit and veg only some of the time
from cross reactivity of tree/plant pollen and foods
give them antihistamine
-usually have history of hayfever
egg alleergy features?
67% grow out of it by 5
can tolerate cooked egg the best, raw the least
usually mild and benign but can be severe
what is the management of an egg allergy?
avoidance
re-introduction
egg ladder: 1. well cooked, 2. lightly cooked, 3. raw
milk allergy features?
rapid pnset
histamine based reaction
symptoms may include b=voimitting and diarrhoea
diagnosis: SPT or SpIgE
non IgE mediated milk allergy features/
not histamine based
baryon presentation; diarrhoea, vomitting, infantile eczema, bloating, PR bleeding
improves with withdrawal of milk protein
ix of non IgE mediated milk allergy?
SPT
history
Specific IgE
therapeutic trial of exclusion under dieticians review
management of milk allergy (some for IgE and non IgE)?
maternal avoidance of cows milk (if breastfeeding also need Ca and vit D supplememts)
EHF formula
if EHF not tolerate use AA formula
soya milk only if >1, or if others not tolerated
