What occurs in type 1 hypersensitivity disorders? Give 3 pathophysiological changes in the body as a result of a reaction.
What is the atopic triad?
Immediate reaction provoked by re-exposure to an allergen. IgE mediated: mast cells release mediators resulting in vasodilation, increased permeability, smooth muscle spasm.
Atopic triad is eczema, asthma and hay fever.
Give some typical symptoms of a type 1 hypersensitivity reaction.
- Angioedema
- Urticaria
- Rhinoconjunctivitis
- Wheeze
- D&V
- Anaphylaxis
Give some disease examples of type 1 hypersensitivity.
Most use skin prick test
- Food allergy
- Atopic dermatitis
- Oral allergy syndrome
- Latex food allergy- food with latex-like components: avocado, banana, potato, tomato, kiwi etc.
- Allergic Rhinitis
- Acute Urticaria- 50% caused by food, drugs, latex, viral infections. 50% idiopathic.
What is anaphylaxis? What are the two immune mechanisms and their triggers?
A severe systemic allergic reaction causing respiratory difficulty and hypotension.
IgE mediated mast cell degranulation- peanut, penicillin, stings, latex.
Non- IgE mediated mast cell degranulation- NSAIDs, IV contrast, opioids, exercise
Give differential diagnoses for anaphylaxis
- C1 inhibitor deficiency- hereditary angioedema
- ACEi induced angioedema
- Acute anxiety
- Urticaria
What is the management for anaphylaxis?
Elevate legs, 100% oxygen, IM adrenaline 500mcg, inhaled bronchodilators, hydrocortisone 200mg IV, chlorphenamine (antihistamine) 10mg IV, IV fluids, Seek help.
