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Nutrition & Disease > Week 10 - Allergy > Flashcards

Week 10 - Allergy Flashcards

1
Q

Food allergy =

A

an abnormal immunological reaction to food

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2
Q

allergen =

A

substance foreign to the body that on interaction with the immune system, causes an allergic reaction

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3
Q

antigen =

A

usually a foreign substance (e.g. protein) that stimulations antibody production.

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4
Q

food intolerance

A

an abnormal reaction to food caused by non-allergic or unknown mechanisms

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5
Q

food aversion

A

strong desires to avoid particular foods

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6
Q

adverse food reaction:

A

any undesired response to food regardless of mechanism

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7
Q

Allergy & Intolerance signs & symptoms

A

hives (uticaria), swelling around mouth, vomiting, diarrhoea, bronchial irritations, rash, bloating

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8
Q

Severe allergic reactions:

A

anaphylaxis

  • difficulty/noisy breathing
  • swelling of the tongue
  • swelling/tightness in throat
  • difficulty talking/hoarse voice
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9
Q

world allergy org estimates what % have food allergy

A

8% - children

2% - adults

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10
Q

allergy risk factors

A

heredity, exposure, GI permeability, environmental factors e.g. microbial exposure

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11
Q

Immune Reaction - food intolerance/allergy

A

food allergy results in an immune response where food intolerance does not.

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12
Q

Type I Hypersensitivity:

A

Allergen (antigen) causes production of antibody immunoglobulin E
> Antigen contacts IgE which are bound to mast cells. Mast cells release mediators (e.g. Histamine)
> Irritant receptors are stimulated resulting in reactions which can lead to anaphylactic shock.

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13
Q

Type IV Hypersensitivity:

A

T-lymphocytes recognise antigens and produce cytotoxic substances that react with the antigen
> reaction occurs dependent on dose (usually). Anaphylactic shock doesn’t occur.

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14
Q

Type I hypersensitivity - associated foods

A

fish, shellfish, nuts, legumes (peanuts), eggs, milk, berries

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15
Q

Type IV hypersensitivity - associated foods

A

Milk, wheat, chocolate, cola, corn, citrus fruit, eggs, beef, white potatoes, pork, legumes, chicken, oatmeal, rye, oranges, cottonseed, mustard, tomatoes, cucumbers, garlic

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16
Q

Reactions to fruits, vegetables, herbs and spices are usually intolerances, but in rare cases can be:

A

allergies

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17
Q

Vitamin D insufficiency is associated with what allergy in infants

A

challenge-proven food allergy

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18
Q

What may be an important protective factor for food allergy in the first year of life:

A

vitamin D sufficiency

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19
Q

Causes of food intolerances include:

A
  • Natural food chemicals (amines, salicylates, glutamate)
  • Enzyme deficiencies (e.g. Lactase, alcohol dehydrogenase)
  • Food additives
20
Q

Amines

A

formed during protein breakdown or fermentation

pineapples, bananas, vegetables, red wine, chocolate, citrus fruits, mature cheeses

21
Q

Salicylates

A

Natural plant chemicals.

Herbs, spices, fruit, vegetables.

22
Q

Glutamates

A

Amino acid

Tomatoes, soy sauce, mushrooms, some cheeses.

23
Q

common additives that people report sensitivity to:

A
  1. Tartrazine (artificial colour)
  2. Benzoic acid (preservative)
  3. Annatto (natural colouring)
  4. Sulfur dioxide/sulfite derivatives (preservative)
  5. Monosodium Glutamate (MSG - flavour enhancer)
24
Q

lactose intolerance depends on

A

lactase presence versus lactose intake

25
Q

Lactose intolerance is caused by:

A

deficiency in the enzyme lactase as a result of:

  • congenital origin
  • gastroenteritis
  • parasitic infection
  • iron deficiency
26
Q

Lactose intolerance affects:

A

approximately 70% of the world’s population.
most common in African, Asian and South American people

approx. 1 in 20 caucasians

27
Q

What is the function of lactase?

A

Lactase separates lactose into glucose + galactose

28
Q

What happens if lactase is not present in sufficient amounts?

A

lactose is not absorbed but instead fermented

Dependent on amount, results in:

  • stomach cramps
  • flatulence
  • diarrhoea with a high water content
29
Q

Zheng et al., 2015: what % of patients with functional GI symptoms reported intolerance to dairy products?

A

50%

30
Q

Diagnosis of food sensitivity:

A

Allergy:

  • skin prick test - trained health professional with a doctor present
  • RAST (IgE blood test) - pathologist

Food Intolerance:
- if allergy is ruled out, a qualified Dietitian can work with a patient to identify food intolerance

Lactose intolerance:
- hydrogen breath test

Coeliac disease:

  • Blood test used to screen for related antibodies.
  • Small bowel biopsy is then essential to confirm diagnosis
31
Q

Comparison: Food Allergy v. Food Intolerance:

A

allergy:
1. Immune response
2. caused by protein allergen
3. mostly children affected
4. usually immediate reaction
5. detected via skin prick test to show antibody production

intolerance:

  1. no immune response
  2. caused by enzyme deficiency, naturally occurring chemicals in food, or food additives
  3. people affected at all ages
  4. often delayed reaction
  5. difficult to diagnose - detailed investigation required (except for lactose intolerance)
32
Q

Coeliac Disease - what:

A

Autoimmune disease that involves a type IV hyperinsensitivity reaction to gluten. Classified as food sensitivity rather than allergy intolerance.
Genetic disorder - HLA DQ2 and HLA DQ8 are the most important genes: 30% of the population carry one or both, but only 1 in 30 will develop coeliac.

33
Q

Coeliac - consequences

A

vilious atrophy in the small intestine

34
Q

Coeliac - associated conditions

A 
Type I diabetes
Autoimmune thyroid disease
anaemia
lactose intolerance
autoimmune hepatitis
multiple sclerosis
infertility
lymphoma
35
Q

Gluten is found in:

A 
wheat
barley
triticale
spelt
rye
oats
36
Q

Proposed explanations for increase in prevalence of food sensitivities (lifestyle factors):

A
  • Hygiene hypothesis
  • Timing of introduction of allergenic foods
  • Processing methods
  • Skin exposure

Other strong associations:

  • Breastfeeding duration
  • Smoking
37
Q

Breast milk contains immunological benefits including:

A
  • T-Cells and B-Lymphocytes
  • T-cell products
  • nonspecific factors e.g. bifidus factor
  • Carrier proteins e.g. lactoferrin, corticoid-binding protein
  • Growth factors and hormones.
38
Q

Hydrolysed formula

A

Prescott review found that a recent RCT showed a reduced risk of allergic manifestations with both partial and extensive hydrolysed formulas.

39
Q

Observation studies showed an association between solid introduction at <3-4 months and:

A

early eczema

40
Q

Hydrolysed formula recommended for:

A

high risk infants if breastfeeding not possible

41
Q

Probiotics:

A
  • Live bacteria that colonise the gastro tract and provide a health benefit to the host.
  • Anti-inflammatory properties that could inhibit type I and type IV hypersensitivity reactions.
  • Non-digestible food components that benefit the host by selectively stimulating growth or activity of bacteria in the colon.
42
Q

Omega-3 group: atopic eczema, egg sensitisation, IgE associated with eczema

A

atopic - lower in O-3 group

egg sensitisation - lower in O-3

IgE: no difference

43
Q

Why is Vitamin D proposed as a factor in the rise of ‘autoimmune’ and ‘allergic’ diseases?

A
  • Due to immunoregulatory effects and declining serum levels.
  • Some evidence of a link between maternal vitamin D status and allergic disease, protective association between decreasing latitude and allergic disease.
44
Q

Preventive strategies:

Insufficient evidence for reduced risk associated with:

A
  1. soy formula use
  2. anthroscopic lifestyle
  3. early life pet exposure
  4. day care attendance
45
Q

LEAP studies:

A
  • 640 infants with severe eczema, egg allergy, or both to consume or avoid peanuts until 60 months of age.
  • prevalence of peanut allergy at 60 months of age was 13.7% in the avoidance group, 1.9% in the consumption group.
  • conclusion: early introduction of peanuts significantly decreased the frequency of the development of peanut allergy among children at high risk
46
Q

LEAP - ON:

A

After LEAP, all participants to avoid peanuts for 12 months.
Peanut allergy higher among participants in the peanut-avoidance group than among those in the peanut-consumption group.

Nutrition & Disease (7 decks)

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