allergy r Flashcards
describe the two phases of an allergic reaction
- mast cell degranulation causing histamine, tryptase and hydrolase release
- inflammatory mediators like prostaglandins, leukotrines and cytokines are released later
effects of histamine
bronchial SM contraction vasodilation pain itch subcutaneous oedema
characteristics of allergy
rapid onset >1hr is unlikely to be allergy histamine mediated urticaria erythema angioedema sweating wheeze improves with antihistamines
features of a mild allergic reaction
urticaria and rash
signs of a severe allergic reaction
angioedema or airway - stridor
bronchospasm - wheeze
hypotension - pallor, red blotches, drowsiness
what children are at a risk of more severe reactions
children with asthma
common triggers of allergic reactions
food environmental allergens drugs stings/bites idiopathic
investigations for allergy
skin prick testing
specific IgE blood test
oral food challenge
considerations for oral food challenge
this is gold standard
needs to be done in a controlled environment that provides close monitoring
antihistamines and epipens need to be readily accessible
management of urticaria and angioedema
avoid triggers
1st line: antihistamines
2nd line: leukotriene antagonist
corticosteroids - short dose
when would tranexamic acid be used
in angioedema
not commonly used
anti-IgE antibody use in allergy
child must be over 7
6 month course
omalizumab is used
presentation of anaphylaxis
laryngeal oedema hypotension bronchospasm feeling of impending doom rapid onset
what is a biphasic reaction
a reaction 1-8hrs after the initial anaphylaxis
give steroids to prevent this and keep patients in hospital overnight
risk factors for anaphylaxis
asthma stress exercise viral infection alcohol
doses of adult and child adrenaline auto-injectors (epipens)
adult 0.3mg
junior 0.15mg
first line treatment for anaphylaxis
adrenaline auto-injectors
actions of adrenaline
reverses peripheral vasodilation decreases angioedema increases peripheral vascular resistance causes bronchodilation decreases release of inflammatory mediators improves BP and coronary perfusion
when should you prescribe an epipen
if the patient had a systemic reaction if allergen is hard to avoid if they have risk factors like asthma if they react to trace amounts if they have idiopathic or exercise induced anaphylaxis
management of anaphylaxis
ABC
adrenaline
antihistamines
steroids
management of allergy
allergen avoidance
antihistamines - use if there is a reaction, not for daily use
adrenaline injectors if indicated
dietary advice - especially in cows milk allergy
optimise asthma control
individualised management plan
egg allergy features
common in infants
grow out of it by 5
mild and benign
how do you manage egg allergy
initial avoidance but then reintroduce egg using egg ladder
features of IgE mediated milk allergy
rapid onset
histamine based
can have vomiting or diarrhoea
identify with skin prick testing or IgE tests
features of non-IgE mediated cows milk allergy
more common
not histamine based
varied presentation - diarrhoea, vomiting, irritability, eczema, bloating, PR bleeding
only diagnostic test is dietary exclusion
management of cows milk allergy
use an alternative formula
work up milk ladder to reintroduce
AA formulas can be used in infants with severe allergy
