Allergic reactions Flashcards
Urticaria Angioedoma Anaphylaxis (22 cards)
What are causes of allergic skin reactions?
- idiopathic
- Food
- Drugs - penicillin, contrast, NSAIDs, morphine, ACEi
- Insect bites
- Contact e.g. latex
- Viral/parasitic inf
- Autoimmune
- Hereditary (angioedema)
Explain the pathophysiology of allergic urticaria
Local increase in permeability of capillaries
Major mediator is histamine from skin mast cells
This can be induced by immunological or non-immunological mechanisms
How does urticaria present?
swelling involving superficial dermis raising the epidermis - itchy wheals (just skin)
what is urticaria also known as?
hives
how does angioedema present?
deeper swelling involving subcut submucosal tissue
of skin and mucosa particalarly eyelids and lips
How does anaphylaxis present?
bronchospasm
facial and laryngeal oedema
hypotension
can initially present as urticaria and angioedema
What is the triple response to histamine?
erythema
wheal
pruritus
What is a wheal?
Localised area of oedema on body surface
What is the most easily recognised cause of urticaria/
Drugs
Sx of drug induced urticaria usually appear within how many hrs?
36hrs of giving drug
Food induced urticaria usually appears within… and in 80% of cases
Within 1 hr after ingestion
GI sx also occuur
what are most common foods associated w anaphylaxis
Peanuts
Tree
Nuts
Shellfish
What is the rx for urticaria?
Non-sedating antihistamines - take a while to work so can give sedating which works quicker quite severe cases
Sedating can be helpful in kids
What is the treatment for severe acute urticaria and angioedema?
Corticosteroids
What are the resp sx of angioedema?
stridor, wheeze, SOB
what s the management of angioedema w/o anaphylaxis?
mild acute angioedema can be treated same as acute urticaria
if not
give slow IV/IM chlorphenamine + hydrocortisone if rapid onset
What is the management of anaphylaxis?
ABCDE
IM adrenaline 1:1000 repeat until adequate response
Then:
- IM/IV chlorphenamine
- IM/IV hydrocortisone
If wheezy - nebulised salbutamol or ipratroprium
What is the inheritance pattern of hereditary angioedema?
autosomal dom
What is the pathophysiology of hereditary angioedema?
Low plasma levels of C1 inhibitor (C1-INH) protein
C1-INH is a multifunctional serine protease inhibitor - probably uncontrolled release of bradykinin resulting in oedema of tissues
What are the sx of hereditary oedema?
painless non-pruritic swelling of subcut/submucosal tissues
no urticaria
attacks may be preceded by painful macular rash
What is the management of hereditary angioedema?
acute: IV C1-inhibitor concentrate, FFP if that isn’t available
What is prophylaxis of hereditary angioedema/
anabolic steroid danazol
