what is the pathophysiology anaphylaxis?
- life-threatening medical emergency caused by severe type 1 hypersensitivity reaction
- IgE stimulates mast cell degranulation causing the release of histamine and other pro-inflammatory chemicals
how does anaphylaxis present?
- exposure of allergen - could be idiopathic
- time between exposure and symptoms, trigger, location and activity
- urticaria
- itching
- angio-oedema around lips and eyes
- wheeze
- swelling of larynx - stridor
- tachycardia
- collapse
- hypotension
- Infant/child: low age specific systolic or >30% drop
- Adolescent: <90mmHg or >30% drop
How is anaphylaxis investigated?
A to E
serum tryptase for mast cell degranulation
how is anaphylaxis managed?
*immediately
- IM adrenaline repeat in 5 mins if required
- antihistamines lie chlorphenamine, cetirizine
- steroids IV hydrocortisone
how is the after event of anaphylaxis managed?
- all children must have period of assessment as biphasic reactions can occur - paeds unit
- serum mast cell tryptase within 6h of event - released during degranulation
- family education of allergen and sign spotting, BLS training
- adrenalin auto-injector - epipen, jext, emerade
- asthma requiring inhaled steroids
- poor access to medical treatment
- adolescents higher risk
- nut, sting allergy
- co-morbidities
how do you administer adrenaline?
prepare device by removing cap, grip device, orange to thigh blue to sky, administer injection, remove device, massage area for 10 seconds, phone ambulance and give second dose in 5 mins if needed
what is the pathophysiology of hayfever?
IgE-mediated type 1 hypersensitivity reaction where environmental allergens cause response in nasal mucosa
*- may be
- seasonal like hayfever
- perennial like house dust mite allergy
- occupational like school or work related
- triggers
- tree pollen or grass
- house dust mites and pets
- mould etc
what is the key features of hay fever?
- runny, blocked and itchy nose
- sneezing
- itchy, red and swollen eyes
- associated with FHx of atopy
- diagnosis history dependent usually
how is hay fever managed?
- clinical
- skin prick maybe useful for pollen, animals and house dust mite allergy
- avoid trigger
- oral antihistamines
- nasal corticosteroid spray
how is nasal spray technique explained?
- hold spray in left when spraying right and right when left
- aim to spray slightly outward away from septum
- do not sniff at same time as spraying - should not taste the spray as gone too far
what is urticaria?
- Acute: <6 weeks; triggers allergy, URTI, idiopathic
- Chronic: >6 weeks; spontaneous or physical triggers
*causes - allergy, physical triggers, prior to menstruation, systemic disease, stress
what are some key examination findings of urticaria?
- purpuric erythematous plaque - coalescing
- potential associated angioedema
- raised pruritic lesions - wheals
- excoriation
- underlying infection signs
- angioedema
what is a red flag symptom of urticaria?
- Associated fever, bruising, joint pain or other or systemic features (need to exclude urticarial vasculitis or chronic urticaria as a manifestation of another disease process)
- Anaphylaxis
- Angioedema
- Age <6 months
- Chronic urticaria (>6 weeks)
what is the management of urticaria?
- history and examination for diagnosis
- In new-onset acute urticaria where assessment does
NOT suggest underlying cause, NO investigation - FBC and CRP if concerned about vasculitis
- acute
- high dose non-sedating antihistamines
- +/- oral glucocorticosteroids
- avoid trigger and aggravating factors
- NSAIDs worsen
- antihistamines to help itching - cetirizine
- single dose of oral prednisolone if severe
chronic
- ongoing - cetirizine increased dose and sedating antihistamine
- immunomodulator therapy if persistent
what is the pathophysiology of allergy?
hypersensitivity of immune system to allergens which are proteins that the immune system recognises as foreign and harmful (types of antigen)
what is a proposed theory of allergy?
- break in the infants skin from eczema or infection that allows allergen like peanut proteins to cross and react with immune system
- child does not have contact with that allergen in GI tract so absence of exposure to allergen
- as it enters through skin recognised as harmful and immune system sensitised to it as harmful
- theory suggests that regular exposure to an allergen and preventing exposure to that allergen through barrier helps prevent allergy
what is key about the presentation of allergy ?
- timing of symptoms after exposure to allergen
- previous and subsequent exposure and reaction to allergen
- symptoms of rash, swelling, breathing difficulty, wheeze and cough
- previous personal and family history of atopic conditions and allergies
what is the initial investigations for allergy ?
skin prick testing
patch testing
RAST
food challenges and testing
