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Medicine: Immunology > Allergy > Flashcards

Allergy Flashcards

1
Q

What type of hypersensitivity reaction is allergy?

A

Type 1 (IgE mediated)

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2
Q

What is atopy?

A

General tendency to produce specific IgE Abs on exposure to common environmental Ags.

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3
Q

What is oral allergy syndrome?

A

Cross-reactivity from pollen allergens to other tings like raw fruit/vegetables.

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4
Q

How can you distinguish between true allergy and oral allergy syndrome?

A
  1. Peanut storage protein (Ara h1-3) present in true allergy.
  2. Pollen cross-reactive peanut protein (Ara h8) present in oral allergy syndrome.
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5
Q

What is the treatment for oral allergy syndrome?

A

Oral histamine (not EpiPen)

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6
Q

What is this describing?

IgE mediated degranulation of mast cells after exposure to: cow’s milk, egg, peanut, tree nut, fish, prawns.

A

True food allergy

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7
Q

What is this describing?
Direct stimulation of mast cells or histamine ingestion. Histamine release by bacterial action. Symptoms mimic an allergic reaction.

A

False food allergy

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8
Q

What is this describing?

Adverse reaction to food with no histamine related symptoms.

A

Food intolerance - lactose intolerance, gluten insensitivity

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9
Q

What is food sensitivity?

A

Umbrella term for: true and false food allergy and food intolerance.

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10
Q

What conditions is atopy strongly associated with?

A

Asthma, allergic rhinitis, eczema.

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11
Q

What are the steps of sensitisation before an allergic reaction?

A
  1. Exposure to allergen.
  2. APC present Ag to Th2 cells
  3. Th2 produces IL-4, IL-13 to stimulate B cells to make IgE.
  4. IgE binds to FC receptors on mast cells.
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12
Q

What are the steps of an allergic reaction?

A
  1. On next encounter of allergen, Ag binds to the IgE.

2. Crosslinking activates the mast cell, release of pre-formed and newly generated mediators.

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13
Q

What are the pre-formed and newly generated mediators in allergic reaction?

A
  1. Pre-formed - histamine, tryptase, heparin.

2. Newly generated - leukotrienes, prostaglandins

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14
Q

What does histamine cause in allergic reaction?

A
  1. Pruritis
  2. Vasodilation and leakage of fluids - hives, angioedema, drop in BP.
  3. Smooth muscle contraction - bronchospasm, wheezing.
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15
Q

What is the effect of histamine on these cells?

  1. Endothelial
  2. Smooth muscle
  3. Mucosa
A
  1. Increased vessel permeability
  2. Constriction of airway
  3. Increased secretion of mucus
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16
Q

How is an allergy diagnosed?

A
  1. Clinical history - time course, triggers, seasonality, location, food or aeroallergens
  2. Allergens for testing selected on the base of history - skin prick, specific IgE, total IgE (least useful).
17
Q

What does a positive result of specific IgE in allergy confirm?

A

IgE sensitisation, may/may not be associated with clinical allergy (need bloods and symptomatic Hx for the diagnosis)

18
Q

What are the important features of skin prick testing?

A
  1. Need a negative and positive control
  2. Wheal >3mm is positive
  3. High compliance (easy to perform)
  4. Antihistamines must be stopped 5d prior to test.
  5. Not advised to patients with extensive eczema.
19
Q

What are the steps of the oral food challenge?

A

Only if skin prick test inconclusive:

  1. Given graded exposure to suspect food under controlled conditions.
  2. Double blind placebo-controlled food challenges are gold standard (except in Hx of anaphylaxis)
  3. Resus equipment needs to be on hand.
20
Q

What is this describing and how is it treated?

Low grade mild infection which activates immune system. Release of histamine in a chronic, random way. Not an allergy.

A
  1. Chronic spontaneous urticaria

2. High dose antihistamines, montelukast.

21
Q

What is the management of a confirmed allergy?

A
  1. Avoid food allergen
  2. Administer emergency treatment if necessary.
  3. Oral non-sedating, long acting antihistamine (loratadine, cetirizine).
  4. Aqueous steroid nasal spray (beclomethasone)
  5. Cromoglicate eye drops/olopatadine eye drops
  6. Pollen avoidance measures
  7. SC pollen immunotherapy if medical treatment fails.

Medicine: Immunology (7 decks)

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