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Paeds - Systemic > Allergy > Flashcards

Allergy Flashcards

1
Q

Compare: allergy, intolerance and atopy.

A
  • Allergy: reaction initiated by specific immunological mechanisms
    • IgE mediated/non-IgE mediated (T cell mediated)
  • Intolerance: reaction initiated by non-immunologic mechanisms
  • Atopy: genetic predisposition to become sensitised
    • Produce IgE in response to ordinary exposures to common environmental allergies
    • May lead to allergic disease - but not always!
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2
Q

Examples of intolerances

A
  • Metabolic e.g. CHO malabsorption- lactose intolerance
  • Pharmacologic e.g. Caffeine causing irritability, restlessness, palpitations
  • Toxic e.g. Food poisoning- salmonella, fish toxins
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3
Q

Examples of atopic diseases

A

asthma, allergic rhino-conjunctivitis, eczema, IgE- mediated food allergy

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4
Q

List 3 major investigations for allergy testing, and state which is the GS.

A
  1. Skin prick test (SPT)
  2. Specific IgE (previously RAST)
  3. Challenge testing (GS)
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5
Q

What is the process for SPT?

A
  • Test that measures the IgE produced in vivo to an allergen
  • Allergen scratched on back, with histamine and saline control
  • Measure at 15 mins
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6
Q

What does the SPT tell you and what doesn’t it tell you?

A 
- What does it tell you? 
	• The larger the SPT size, the more likely an IgE mediated reaction will occur
- What does it NOT tell you
	• Severity of reaction
	• Non-IgE mediated reaction
  • Importantly +ve SPT doesn’t equal allergy, so called ‘clinically silent sensitisation’
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7
Q

Pros and cos of the SPT?

A

○ Pros: readily available, inexpensive, no minimum age

○ Cons: only available to allergists

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8
Q

When will you get a false positive with an SPT?

A
  • recent anti-histamines (H1 only) - withold for 3-4 days

- Recent anaphylaxis (SPT > 6 weeks later)

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9
Q

What is considered a +ve result with an SPT? What is a convincing result for peanut allergy?

A

○ +ve SPT: wheal and flare > 3mm cf saline control

○ Convincing result for peanuts - >7mm wheal

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10
Q

What does the specific IgE test test?

A
  • Detects free antigen specific IgE in serum
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11
Q

Pros and cons of specific IgE test

A
  • One step above, but:
    ○ less sensitive than SPT - more false negatives
    ○ More expensive
  • Pros:
    ○ Useful if pt on anti-histamines
    ○ If dangerous to do SPT
    ○ Can use if SPT allergens not available
    ○ Can do a blood specific IgE e.g. to peanuts
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12
Q

Mx of a generalised allergic reaction: acute and ongoing

A
  • Anti-histamines
  • Cool compress
  • Observation
  • Identify trigger
  • Allergy action plan
  • Education
  • Referral
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13
Q

What are the types of allergic rhinitis? Describe.

A

Seasonal allergic rhinitis:
• due to pollen allergy, esp grass in Aus
• Symptoms start abruptly in spring and continue for a variable time, depending on the geographical area.
• Symptoms are worse outdoors.

Perennial allergic rhinitis:
• usually due to house dust mite allergy, others e.g. animal dander
• Symptoms are often worse at night or early in the morning.

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14
Q

What are some possible consequences of serious cases of allergic rhinitis?

A
  • increase the chance of sinus infections
  • affect learning and performance in children
  • lead to bad breath, a husky voice and/or a sore throat
  • more frequent eye infections because people rub itchy eye
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15
Q

What are some clinical features of allergic rhinitis?

A

Nasal symptoms:
• Sneezing, itchy nose, itchy palate
• Rhinorrhoea
• Nasal obstruction - snoring, mouth breathing

Eye symptoms:
• Intense itching, hyperaemia, watering, chemosis, periorbital oedema

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16
Q

What Rx can be used to manage allergic rhinitis? What isn’t recommended?

A

• Oral antihistamines (e.g. cetirizine, loratadine)
○ manage itching and sneezing or eye symptoms

• Intranasal corticosteroids (e.g. mometasone, fluticasone)
○ First line for perennial and seasonal allergic rhinitis

  • Allergen immunotherapy (3-5 year program)
  • NB - nasal decongestant not recommended
17
Q

Compare food allergy vs food intolerance.

A
  • Food allergy
    • immune mediated
    • “Reproducible, non-dose dependent” immunological reaction to food proteins by exposure to a defined stimulus that causes an adverse clinical reaction, at a dose tolerated by normal person
  • Food intolerance - NOT immune mediated
18
Q

Compare IgE vs non-IgE mediated food allergies.

A

IgE:

  • Generalised anaphylaxis
  • Pathophys: IgE induced mast cell degranulation
  • Rapid onset (<2h)
  • Ix: SPT/RAST, food challenge

non-IgE:

  • mainly GI/skin features
  • T-cell mediated
  • Intermediate (2-24h)/delayed (>24h) onset
  • Ix: Patch test, food challenge
19
Q

What are the major food groups causing food allergies? Which are hard to outgrow?

A 
8 major food groups cause >90% of food allergy: 
• Soy 
• Eggs - earliest onset
• Milk - earliest onset
• Fish
• Wheat
• Shellfish - can have later onset
• Tree nuts*
• Peanuts *

*= hard to outgrow

20
Q

Outline a quick history for food allergy.

A
  • What was ingested?
    • Food type
    • Form
  • Amount ingested?
  • How was it cooked/was it raw?
  • Timing of exposure to reaction onset/offset
  • How serious was the reaction? Sx of allergy?
  • Treatment needed
  • Previous exposures? Is it reproducible?
  • FHx of allergy, PHx allergy/atopy
  • High risk groups for anaphylaxis
21
Q

List some conditions caused by non-IgE mediated food allergy.

A
  • FPIES (food protein induced enterocolitis syndrome)
  • FPIE (food protein induced enteropathy)
  • Food protein induced proctocolitis
  • Eosinophilic oesophagitis
22
Q

FPIES:

  • What age
  • Which food
  • Presentation
  • Mx
A
  • Weeks-months, outgrown by 3-4yo
  • Common trigger cow’s milk, but almost any food can
  • Acutely unwell: vomiting, blood diarrhoea, CV collapse: hypotension/pallor
  • FFT

Mx:

  • IV fluid resuscitation
  • IM adrenaline is NOT used to treat this reaction
23
Q

FPIE:

  • What age
  • Which food
  • Presentation
A
  • Early infancy
  • Cow’s milk
  • Unwell: vomiting, diarrhoea, oedema, FTT, abdo distention
24
Q

Food protein induced proctocolitis:

  • What age
  • Which food
  • Presentation
A
  • Early infancy
  • Cow’s milk, soy milk, BF
  • WELL baby - blood streaks in stool
25
Q

Eosinophilic oesophagitis:

  • Histopath
  • Presentation
  • Which food
A 
- Eosinophilic infiltration of oesophageal mucosa 
• Variable and age-dependent presenting features
	• Regurgitation/vomiting
	• Slow eater/food refusal
	• Failure to thrive 
	• Difficulty swallowing
	• Food impaction
	• Epigastric pain 
- dairy, wheat, egg, soy
26
Q

Mx of Food allergies

A
  • Education – Natural history
  • Dietary avoidance
  • Action plan for accidental exposure
  • Consider Epipen, Medicalert bracelet
  • Yearly review
  • Manage and control co-morbid asthma
  • Repeat SPT/RAST (12 monthly) or re-challenge 6-12mo
27
Q

Describe the features of insect allergies with varying severities.

A
  1. Normal: redness, swelling up to 5-10cm, transient (resolve few to 24hrs)
  2. Large local reaction: swelling>10cm developing minutes to hrs after the sting and lasting over 24hrs +/- systemic upset.
  3. Systemic (anaphylaxis):
    a. Mild – no cardiovascular sx
    b. Mod/Severe – with CVS sx
  4. Toxic: from multiple stings, due to high concentrations of histamine-like substances.
28
Q

Venom immunotherapy:

  • When can one receive it
  • How long is the therapy
  • Risk of anaphylaxis?
A
  • Only with evidence of:
    ○ specific IgE (skin or RAST test)
    ○ + systemic reaction with cardiorespiratory involvement.
  • Induction + maintenance: 3-5years
  • 10-15% experience systemic reactions during early weeks of treatment
29
Q

What is important to remember regarding PHx hypotensive reaction with insect allergy?

A

40% will have immediate systemic allergic reaction on subsequent stings

Paeds - Systemic (18 decks)

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