Allergy

Question 1

Define allergic rhinitis

Answer 1

Inflammation of nasal epithelium in resonse to allergen

• results in characteristic sneezing, coughing, rhinorrhoea and red itchy eyes
• hayfever

Question 2

Pathophysiology of allergic rhinitis

Answer 2

Abnormal IgE-mediated immune response to an allergen - type 1 hypersensitivity reaction
Early phase
- IgE-mediated mast cell degranulation releases histamine directly causing allergic effects
Late phase
- 4-6 hours later eosinophils, basophils and T cells release mediators that cause nasal inflammation

Question 3

Mx of allergic rhinitis

Answer 3

Limit allergen exposure
Non-sedating antihistamines - loratadine, fexofenadine
Sodium cromoglycate drops
Severe cases may require systemic leukotriene receptor antagonists - montelukast
Management of other ectopic conditions

Question 4

Pathophysiology of food allergy

Answer 4

IgE mediated
- mast cell degranulation in food allergy acts systemically to produce range of symptoms - urticaria, angioedema and bronchospasm
Allergy may be primary or secondary
- primary = never developed immune tolerance to substance
- secondary = child previously tolerated substance but has developed cross-sensitivity intolerance - tend to be less severe

Question 5

Epidemiology of food allergy

Answer 5

6% of children - falls to 2% of adulthood

Most commonly nuts, milk, eggs, seafood, seeds and fruits

Question 6

Risk factors of food allergy

Answer 6

Fhx

Non-breastfed infant

Question 7

Clinical features of food allergy

Answer 7

Onset of symptoms 10-15 mins after food ingestion
Typically urticaria and rash
Anaphylaxis - angioedema of face, voice change, sensation of tight chest and cough/wheeze, stridor

Question 8

Ix for food allergy

Answer 8

Skin prick testing

• suspected allergens put into skin using sterile needle with control substance (histamine)
• areas that redden suggest IgE mediated allergy

Question 9

DDx of food allergy

Answer 9

Food intolerance

- presents with diarrhoea/vomiting or abdo pain/colic - non IgE mediate

Question 10

Mx of food allergy

Answer 10

Anaphylaxis
- ABCDE
- high flow O2
- IM adrenaline 1:1000 - 0.15ml up to 6 yrs, 0.3 ml up to 12 years
- 20ml/kg IV fluid bolus
- IV hydrocortisone
- IV chlorphenamine
- salbutamol nebulisers for bronchospasm
Long term
- education on avoiding offending allergens
- EpiPen and education on use
- dietiticain input if multiple allergies/failure to thrive
- testing to identify other allergens