Allergy

Question 1

Allergies:
- Definition
- Symptoms
- Investigations
- Management

Question 2

Anaphylaxis:
- Definition
- Causes (6)
- Risk factors (3)
- Symptoms (10)
- Signs (3)
- Management
- Investigations
- Complications (3)

Answer 2

Anaphylaxis:

• Definition: life threatening type 1 hypersensitivity reaction to an allergen involving airway, breathing and circulation
• Causes: drugs (abx, nsaids), radiocontrast dye injections, venom bees/wasps, foods (shellfish, nuts, egg), exercise induced, idiopathic
• Risk factors: asthma, mast cell disorders, increased exposure to allergens
• Symptoms: stridor, cough, hoarse voice (lip/pharynx swelling), dyspnoea (laryngeal oedema + bronchoconstriction), clammy skin, drowsy, shock (peripheral vasodilation + inc perm causes plasma leakage from circulation + dec intravasc volume), abdo cramping, D+V, pruritis
• Signs: urticaria/angiooedema/erythema, wheeze, hypoxia
• Management: call help, remove factors/lie flat, A-E, IM adrenaline 1:1000 (500 micrograms/0.5mg if >12, 300 if 6-12, 6mnths - 6yrs 150, <6 mnths 100-150) and repeat every 5 mins (adrenergic action inc bp and b agonist action inc cardic contract/hr/bronchodil), high flow oxy, IV fluid bolus, bronchodilators via neb salbut/vent support
  If <16 admit as biphasic anaphylaxis can occur within 72 hours
• Investigations: confirm via serum mast cell tryptase within 6 hours
• Complications: anaphylactic shock (not enough oxy being delivered to tissues) hence resp and cardio failure, arrhythmias AF, refractory anaphylaxis (no improvement after 2 rounds adrenaline so need adrenaline infusion)

Question 3

Urticaria:
- Definition
- Pathophysiology
- Causes (3)
- Investigations
- Management
- DD (2)
- Complications (2)

Answer 3

Urticaria:

• Definition: skin condition where transient raised pruritic lesions (wheals), is acute when <6 weeks (usually resolve in 24 hours) due to allergy and chronic is >6 due to autoimmune
• Pathophysiology: reaction in superficial epidermis. Angiooedema is deeper form which affects dermis
• Causes: food within 1-2 hours, meds, insect stings
• Investigations: bloods (lfts, tfts, crp, fbc), allergy testing >8mm, oral food challenge
• Management: self limiting, remove triggers, symptom diary, cool compresses, non-sedating antihistamines cetirizine for max 6 weeks unless if chronic then 3-6 months. If severe oral corticosteroids. Third line is LTRA, biologics
• DD: atopic eczema, contact dermatitis
• Complications: angiooedema, anaphylaxis

Question 4

Allergic rhinitis:
- Definition
- Symptoms
- Investigations (2)
- Management
- Complications

Answer 4

Allergic rhinitis:

• Definition: igE mediated inflammatory disorder where nasal mucosa becomes exposed and sensitised to allergens. When this is seasonal and due to tree pollen or grass = hayfever
  Atopy is predisposition to having hypersensitivity reactions
• Symptoms: swollen/running/red eyes, sneezing, nasal itch/runny
• Investigations: skin prick testing, serum specific IgE
• Management: nasal irrigation with saline, intranasal antihistamine as needed, regular intranasal corticosteroid, trigger avoidance, don’t dry clothes outside, shut windows, shower after outdoors
  If severe 10-15mg 3-7 days oral corticosteroids
  Safety net: if resp distress/ cyanosis 999
• Complications: impaired school performance