Allergy Flashcards Preview

Paeds - Systemic > Allergy > Flashcards

Flashcards in Allergy Deck (29):
1

Compare: allergy, intolerance and atopy.

- 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!

2

Examples of intolerances

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

3

Examples of atopic diseases

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

4

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

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

5

What is the process for SPT?

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

6

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

- 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'

7

Pros and cos of the SPT?

○ Pros: readily available, inexpensive, no minimum age
○ Cons: only available to allergists

8

When will you get a false positive with an SPT?

- recent anti-histamines (H1 only) - withold for 3-4 days
- Recent anaphylaxis (SPT > 6 weeks later)

9

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

○ +ve SPT: wheal and flare > 3mm cf saline control
○ Convincing result for peanuts - >7mm wheal

10

What does the specific IgE test test?

- Detects free antigen specific IgE in serum

11

Pros and cons of specific IgE test

- 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

12

Mx of a generalised allergic reaction: acute and ongoing

- Anti-histamines
- Cool compress
- Observation
- Identify trigger

- Allergy action plan
- Education
- Referral

13

What are the types of allergic rhinitis? Describe.

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.

14

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

• 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

15

What are some clinical features of allergic rhinitis?

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

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

16

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

• 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

Compare food allergy vs food intolerance.

- 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

Compare IgE vs non-IgE mediated food allergies.

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

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

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

Outline a quick history for food allergy.

- 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

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

- FPIES (food protein induced enterocolitis syndrome)
- FPIE (food protein induced enteropathy)
- Food protein induced proctocolitis
- Eosinophilic oesophagitis

22

FPIES:
- What age
- Which food
- Presentation
- Mx

- 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

FPIE:
- What age
- Which food
- Presentation

- Early infancy
- Cow's milk
- Unwell: vomiting, diarrhoea, oedema, FTT, abdo distention

24

Food protein induced proctocolitis:
- What age
- Which food
- Presentation

- Early infancy
- Cow's milk, soy milk, BF
- WELL baby - blood streaks in stool

25

Eosinophilic oesophagitis:
- Histopath
- Presentation
- Which food

- 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

Mx of Food allergies

- 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

Describe the features of insect allergies with varying severities.

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

Venom immunotherapy:
- When can one receive it
- How long is the therapy
- Risk of anaphylaxis?

- 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

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

40% will have immediate systemic allergic reaction on subsequent stings