allergy

Question 1

what is type I hypersensitivity?

Answer 1

IgE mediated immediate hypersensitivity

Question 2

what are signs and symptoms of an allergy?

Answer 2

urticaria
swelling
nausea
vomiting
cramps

Question 3

during an allergy what happens with cells?

Answer 3

1. allergen binds to IgE
2. cross linking through allergen exposure leads to mast cell activation
3. degranulation and inflammatory mediator release
   histamine and leukotriene relase

Question 4

what is the effect of histamine?

Answer 4

endothelial cells: vessel permeability
smooth muscle: contraction of smooth muscle and airway vasoconstriction
mucosal epithelial lining: increased secretion of mucus

Question 5

what is anaphylaxis?

Answer 5

a severe systemic allergic reaction

• respiratory difficulty
• hypotension

Question 6

what blood tests can be done for allergy?

Answer 6

serum allergic specific IgE concentrations

Question 7

what is a useful measurement after suspected anaphylaxis/

Answer 7

serum tryptase
released during mast cell degranulation

should be taken between 15 minutes and 3 hours after the reaction

Question 8

what does skin prick testing test?

Answer 8

the response to the allergen being tested

Question 9

what are advantages of skin prick testing?

Answer 9

painless
low risk of side effects
good patient complience

Question 10

what are disadvantages of skin prick testing?

Answer 10

if the pt has took antihistamines it may suppress wheal and flare reaction
less reliable for food allergens compared to inhaled
discomfort

Question 11

why might an oral food challenge be offered

Answer 11

unclear history of food allergen

blood test and skin tests are inconclusive

Question 12

what is the management of hayfever?

Answer 12

1. non sedating long acting oral antihistamines: loratidine or cetirizine
2. aq steroid spray

eye drops

pollen avoidance

Question 13

what are the three criteria to anaphylaxis?

Answer 13

1. sudden onset and rapid progression of symptoms
2. life threatening compromise of airway/breathing/circulation
3. skin or mucosal changes: flushing/ urticaria/angiodema

Question 14

what are the actions of adrenaline?

Answer 14

smooth muscle relaxation

vasoconstriction

Question 15

what is the management of anaphylaxis?

Answer 15

1. remove allergen
   2, preserve airway and give high flow oxygen
2. adrenaline 0.5ml of a 1:1000 solution ie 0.5mg IM
   repeat after 5 minutes if needed
3. fluid challenge 500-1000ml
4. chlorphenamine 10mg
5. hydrocortisone 200mg

observe for 6-12 hours
measure mast cell treatment after emergency treatment and again 2 hours later

Question 16

what are types of hypersensitivity reaction?

Answer 16

1. immediate IgE allergy mediated
2. Cytotoxic IgG/IgM complement activity
3. immune complex IgG
4. delayed hypersensitivity t cell mediated

Question 17

what is the correct dose of anaphylaxis medications in <6 months, 6 months-6 years, 6-12 years and >12 and adults?

Answer 17

<6 months:
150 micrograms adrenaline
25mg hydrocortisone
250micrograms/kg chlorphenamine

6months-6 years:
150 micrograms
50mg hydrocortisone
1.5mg chlorphenamine

6-12 years:
300 micrograms adrenaline
100 mg hydrocortisone
5 mg chlorphenamine

> 12 and adults:
500 microgrames adrenaline
200mg hydrocortisone
10mg chlorphenamine

Question 18

where do you teach patients to used an epipen?

Answer 18

anteriolateral aspect of the middle thigh