1: Immunology, Allergy - Anaphylaxis Flashcards
Define anaphylaxis
Life-threatening allergic event due to immediate hypersensitivity reaction
What is the most common cause of anaphylaxis in children
Food substances
What food-types can cause anaphylaxis
- Peanuts
- Eggs
- Shellfish
What are other triggers for anaphylaxis
Medication (Penicillin)
Stings, Bites
Injections - radiocontrast dye
Describe clinical presentation of anaphylaxis
Skin: Urticaria, Angioedema
Resp: Airway obstruction - bronchospasm, laryngeal oedema
GI: diarrhoea, abdo cramps
Systemic shock
Explain pathophysiology of anaphylaxis
IgE cross-link mast cells to cause release of histamine. Which causes smooth muscle contraction and peripheral vasodilation - leading to bronchospasm, abdominal cramps.
Describe approach to anaphylaxis patient
- Contact resus team
- A-E approach
- Lie patient on their back with their legs raised
What 3 medications are given in anaphylaxis
- IM adrenaline
- IV chlorphenamine
- IV hydrocortisone
If adrenaline is ineffective, when can second-dose be given
5-minutes later
Aside from chlorphenamine, hydrocortisone and adrenaline - what other interventions are given for anaphylaxis
Remove stimulus
Oxygen
IV Fluids
When is salbutamol indicated for anaphylaxis
If individual is having bronchospasm
Outline management of anaphylaxis
- Contact resus team
- Oxygen
- IM adrenaline
- IV Fluid
- IV hydrocortisone
- IV chlorphenamine
What blood should be taken following anaphylaxis
Mast cell tryptase
When is mast cell tryptase taken
1-2h later
How long should patients be observed for following anaphylaxis and why
Observe patients for 6-hours: due to risk of biphasic attack
What should all individuals be trained how to do before discharge
Use epipen
What is in an epipen
0.3mg Adrenaline (1:1000)
What does of adrenaline is given 6m -6 years
0.15mL (150mcg)
How many grams of adrenaline are in 0.15mL
150mcg
What dose of adrenaline is given 6-12 years
0.3mL (300mcg)
What dose of adrenaline is given above 12 years
0.5 mL (500mcg)
What dose of hydrocortisone is used if under 6-months
25mcg
What dose of hydrocortisone is used if 6-months to 6-years
50mcg
What dose of hydrocortisone is used if 6 years to 12 years
100mcg
What dose of hydrocortisone is used if more than 12 years
200mcg
What dose chlorphenamine is given 6m-6 years
2.5mg
What dose chlorphenamine is given 6-years to 12-years
5mg
What dose chlorphenamine is given after 12-years
10mg
What is allergy
type I, IgE mediated reaction
What is true food allergy
IgE mediated hypersensitivity reaction to food
What can cause allergies
- Food
- Medication
- Dust mite
- Pollen
- Fur
What foods commonly cause allergies
- Seafood
- Peanuts
- Soy
- Eggs
What is a risk factor for allergy
FH of atopy
What is atopy
Genetic tendency to produce IgE
What is protective against allergy
Breast feeding before age-1
What are symptoms of allergy
- Mouth breathing: snoring, apnoea
- Allergic conjunctivitis
- Wheeze
What is a sign of allergy
- Atopic eczema
How do food allergies usually present in children
- Diarrhoea w/ blood and mucus in stools
- Vomiting
- GORD
- FTT
- Urticaria
- Peri-oral erythematous rash
When should food allergy be considered
If children with: GORD, Chronic constipation or eczema do not response to treatment
how do allergies usually present in childhood
Allergic march:
- In infancy present with rash and food allergies
- In childhood present with conjunctivitis, asthma and rhinitis
what is pan-allergy syndrome
There are pan-allergens in plants that can trigger an autoimmune reaction. These allergens are heat-labile and destroyed in stomach: hence cause limited oral symptoms
what is false-allergy syndrome
Direct degranulation mast-cells without use IgE
what is food intolerance
Adverse reaction to food, with no IgE mediate symptoms
What are the 3 methods to identify allergies
- Skin Prick Test
- Specific IgE testing
- Total IgE
What is skin-prick testing
A prick is made in the volar aspect of the arm and a allergen inserted
What are two contraindications to skin-prick testing
Eczema
Anti-histamines
How long should antihistamines be stopped prior to skin prick testing
6-7 days
What is used as the positive control
Histamine
What is used as the negative control
Water
What is a positive skin prick testing in children
> 3mm
What is serum-specific IgE also called
Radio allergen absorbent testing (RAST)
What is the RAST test
Looks for proteins to specific allergens
How is the RAST test graded?
0-6
6 = strongly positive
What does it mean if the RAST test is positive
It means individual is sensitised to an allergen, it does NOT mean they have clinical allergy
What does a positive total serum IgE indicate and what does this mean in practice
Individual is atopic. Therefore should not be used to screen for allergy
In cases where allergens cannot be identified what is offered
Elimination diet
Explain the elimination diet
Individuals are given a few hypoallergenic foods for 1-2W then other foods are gradually re-introduced
What is first-line for food allergy
Exclude food
What is used to manage allergy acutely
Anti-histamine
If a child has had 6- 12 months symptom-free on exclusion diet what is considered
Food challenge (in hospital setting where anaphylaxis can be controlled for)
When do infantile food allergies tend to resolve
2-years
What allergy tends to persist
Peanut allergy
Define cow’s milk protein allergy
IgE-mediated reaction to proteins in cow’s milk
Define cow’s milk protein intolerance
Mild-moderate delayed reaction to cow’s milk
When does cow’s milk protein allergy occur
0-3 months
What is a major risk factor for cow’s milk protein allergy
Bottle feeding.
Cow’s milk protein allergy is extremely rare in formula fed infants
When is cows milk protein allergy rarely seen
In breast-fed infants
What are symptoms of cows milk protein allergy
- Urticaria
- Atopic eczema
- Wheeze
- Persistent cough
- Itchy throat
- Angioedema
- Anaphylaxis
What are symptoms of cow’s milk protein intolerance
- Diarrhoea
- Vomiting
- regurgitation
- colic: crying and irritability
how is cow’s milk protein allergy usually diagnosed
Clinically - often on cessation of symptoms on exclusion of cows milk protein
in formula-fed infants how are is mild-moderate CMPA managed
Extensively hydrolysed formula (EHF)
in formula-fed infants, how is severe CMPA managed
Amino acid based formula
What are indications for amino acid based formula
No response to extensively hydrolysed formula
Explain how cow’s milk protein allergy is managed in breast-fed infants
- Encourage mum to continue breast feeding but exclude dairy products from her diet
What should be given to mum if child has cow’s milk protein allergy
Calcium supplementation
When breast-feeding stops, what should an infant be put on in CMPA
After breast feeding put on EHF for at least 6-months
What should be considered 6-12m after CMPA
CMP challenge
What % of children with CMPA will be tolerant by 5-years
55%
When will children with cows milk protein intolerance be tolerant
3-years